China has been on the stage of rapid development of urban tourism since 1980 s. The status change of urban tourism destinations is continuous and drastic during this period. Some traditional tourist cities continue to be the most important destinations in China, some have developed very rapidly in the past and ranked top ten urban destinations but the others developed slowly and dropped in ranking. This paper systematically analyzes the reasons of the status change of urban tourism destinations and explores how a big city develops urban tourism focus on the analysis on the impacts of the evolution of urban functions on urban tourism development. Based on comparative analysis on tourist arrivals and tourist income of Guangzhou city and Xi'an city, this paper argues that urban tourism in Guangzhou city is significantly on the structural growth where tourist arrivals grow weakly but tourist income increases rapidly. This paper further explores and explains the driving force of structural growth in urban tourism of big cities. So on the one hand, big city should enhance tourism related urban functions, such as political, culture, modern service, transportation,business function, in order to make a structural growth of urban tourism. On the other hand, a higher concentration of urban function could lead to city disease, such as traffic jam, pollution, crowded and rising prices which will result in deterioration of city image and tourists' satisfaction. So the enhancement of urban functions is a double-edged sword. All the big cities should have correct views of the relationship between enhancement of urban functions and structural growth of urban tourism.