In the context of global warming, the number of days in summer heat has increased significantly and the heat island effect caused by urbanization has aggravated the situation. As a result, summer tourism has been the most popular tourism product. This article, on the basis of summarizing the relevant researches and practices both domestic and overseas, holds the point that comfortable and cool climate in summer is just a basic condition for the development of summer tourism. Moreover, it offers the creative ideas of taking extra emphasis on the industrial development. Through systematically analyzing the impact factors of summer tourism, the author tried to build the concept model of city summer tourism index. And then, indicators such as weather comfortable degree, leisure degree, tourist satisfaction and comprehensive risk degree have been established. Weather comfortable degree is an indicator to evaluate the weather condition of destination. Through the confirmation of weather comfortable index, tourists satisfaction index, leisure degree index, comprehensive risk degree index and the index weight of each one, five levels have been classified. In this way, the situation of city tourism for summer can be clearly evaluated. Summer tourism assessment indicators system functions as a framework for the assessment of the conditions of a summer tourism destination, to help the tourists to make a right decision and provide operative management tools for summer tourism development. The framework discussed in this paper has to be practiced and improved. The authors will do this research through investigation of sixty cities in China, and publish research reports about this work. The indicators will be built more complete and evaluated more accurate and reliable.