Countries and regions around the South China Sea are not only important hubs for the construction and development of the Maritime Silk Road, but also an important platform for international cooperation. However, due to the differences in natural conditions, social and economic bases, and urban development stages in the region, the internal urbanization process and the urban system pattern remarkably vary among different countries. Based on the population data from 1960 to 2020, this paper presents an empirical study on the spatio-temporal characteristics of urbanization in the countries (regions) around the South China Sea. Using indicators of urban primacy index and Gini coefficient, the study yields several findings. First, while most of the countries (regions) are in later stages of urbanization, there are great differences in the levels of urbanization among these countries (regions). Second, the spatial structure of urban system in the region is dominated by strong single center structure, and there are few countries and regions with double (multi) center structure. The internal structures of urban systems have been evolved in an unbalanced manner, in the way that most countries have a high degree of urban primacy. Thirdly, The phenomenon of population spatial agglomeration in major cities is significant, and there is a tendency to further agglomeration and development.

The South China Sea Rim is an important cooperation platform for promoting the "Maritime Silk Road" initiative in the new era. This paper selects 16 cities with a population of more than 300,000 in China and Southeast Asia as the research objects, and uses urban built-up land data from 1990 to 2018, as well as the urban land density function and public edge measurement method to calculate the urban spatial growth rate and land expansion model in each period, and briefly discusses the relationship between urban spatial expansion, population, and industry in each period. The following are the primary conclusions:1) From 1990 to 2018, the urban land expansion rates of Guangzhou, Vientiane, Manila, Singapore, Shenzhen, Hanoi, and Hong Kong remained at a medium and low-speed steady growth rate of 1% per year, while those of Jakarta, Phnom Penh, Kuala Lumpur, Bangkok, and Zhuhai slowed after the end of the twenty-first century. 2) In terms of urban land expansion patterns, 16 cities have grown in the last 30 years through exterior expansion and internal infill. 3) The population of 16 typical cities in the South China Sea has a high positive correlation with the number and pace of urban land area increases, indicating that the population and land expansion of these 16 cities in the South China Sea are on par.

The globalization process promotes the formation of a city network in which each city connects with and evolves upon interactive flows. International airlines and flights undertake cross-boundary flows of both social elite as the carriers of capital and innovation and goods with high added value. On this basis, international airlines and flights are key aspects in revealing the interactions among high-level cities and thereby becoming a subject of intense research on city networks. Applying social network and ArcGIS analysis based on a collection of data on international passenger and cargo airlines and flights within the South China Sea region in 2000, 2010, and 2018, this study examines the network structure and spatial pattern evolutions of both international air passenger and cargo networks in this transnational region. Taking air passenger and cargo networks together, Hong Kong (HKG) and Singapore (SIN) have been the two transnational airport hubs all through the 2000-2018 period, while Shanghai (PVG), Shenzhen (SZX), Taipei (TPE), and Bangkok (BKK) have emerged as the new transnational passenger and cargo airport hubs recently. Meanwhile, Singapore (SIN) has strengthened its role in the passenger network along with Kuala Lumpur (KUL), Guangzhou (CAN) and Macau (MFM), whereas Hong Kong (HKG) has played an increasingly important role in the cargo network with Chongqing (CGK), Ho Chi Minh (SGN) and Hanoi (HAN).

The countries (regions) surrounding the South China Sea are of great significance to China's national security and foreign cooperation. This paper reveals the trade competitiveness and complementarities between China and the countries (regions) surrounding the South China Sea, contributing to the understanding of the regional economic relationship in China from the perspective of competition and cooperation. The results show that:1) The trade scale between Chinese mainland and the countries (regions) surrounding the South China Sea is increasing. China and Hongkong, Taiwan, Vietnam, Philippines, Singapore and Thailand have higher export similarity, stronger trade competition in the world market, and the degree of competition with Hongkong tends to decline, and the degree of trade competition with Taiwan and Vietnam tends to be enhanced. 2) Compared with other countries (regions) surrounding the South China Sea, China has strong competitiveness in SITC5 (Chemicals and related products, n.e.s.), SITC7 (Machinery and transport equipment), SITC6 (Manufactured goods classified chiefly by material). 3) The trade competitiveness between China and the countries (regions) surrounding the South China Sea is gradually increasing, especially with the Philippines and Vietnam.

Based on throughput data of China's coastal ports from 2004 to 2019, this paper use HHI index, gravity model to compare competition and cooperation of five coastal port clusters. Combined with the route data of world's top10 shipping companies in 2019, the spatial pattern of port groups participating in the world's eight shipping regions is described through social network analysis. The results show that internal competition has intensified, among which the Pearl River Delta port cluster, Yangtze River Delta port cluster and the Bohai Rim ports cluster have formed multi-center hub competition mode, while the Southeast coastal ports cluster is still oligopoly concentrated, and the Southwest coastal ports cluster is still in the stage of multi-port competition. The oligarchic ports such as the port of Shanghai, Shenzhen, Hong Kong and Qingdao, play a major role in the external relations. The spatial connections are significantly different. The ports clusters of the Yangtze River Delta and the Pearl River Delta have established relatively close shipping links with the eight major shipping regions, while the southeast and southwest coastal port clusters have a low degree of external contact. The port groups need to optimize the internal development pattern to meet the unknown opportunities and challenges of globalization.