At present, when the economic development has entered a new normal, it is of great significance for China's tourism industry upgrading and sustainable economic development to explore the development trend of tourism industry in China's urban agglomerations and the climbing law of tourism industry competitiveness. The formation and development process of urban agglomeration is also accompanied by the development process of urban agglomeration tourism industry, which shows that with the passage of time and the "competition-cooperation game" of inter-city tourism industry, the competitiveness of urban agglomeration tourism industry is gradually rising. In this study, the geometric expression of the evolution law of tourism industry competitiveness in urban agglomerations is obtained by constructing a mathematical model, and the evaluation index system of tourism industry competitiveness in urban agglomerations is constructed based on six criteria layers of the improved diamond model. The competitiveness scores of tourism industry in cities of urban agglomerations in China are calculated by using CRITIC objective weighting method, and the comprehensive scores of tourism industry competitiveness in 19 urban agglomerations in China are calculated by using weighted average method, and descriptive statistical analysis and global spatio-temporal evolution analysis are carried out. Finally, the method of simulation verification is used to fit and verify the climbing law of tourism industry competitiveness in China's urban agglomerations, and then explore the development path of tourism industry competitiveness in China's urban agglomerations. Through the above research, the following three basic conclusions can be drawn: 1) The competitiveness of tourism industry in China's urban agglomerations shows a stepwise upward trend in time series, and the central cities of urban agglomerations are constantly playing a "competition and cooperation game" with surrounding cities to form an urban agglomeration tourism industry community, thus promoting the overall competitiveness of tourism industry in urban agglomerations. However, this rising state is not strictly regular, and sometimes it does not significantly improve or even decrease; 2) By 2018, the competitiveness of tourism industry in urban agglomerations in China has been improved to varying degrees. In this study, the competitiveness of tourism industry in urban agglomerations is divided into five levels. With the change of time series, the competitiveness level of tourism industry in urban agglomerations has been improved. The average climbing rate of tourism industry competitiveness of Chinese urban agglomerations is 4.38%, among which the national urban agglomerations have the highest climbing rate, followed by regional urban agglomerations, and the regional urban agglomerations have the lowest climbing rate. In China's urban agglomerations, the competitiveness of urban tourism industry around Hu Huanyong Line is the strongest, and the competitiveness of urban tourism industry in the eastern region is slightly better than that in the western cities. The highly competitive cities, which are mainly national central cities, urban agglomeration central cities and provincial capital cities, show a "stepwise" decline towards the surrounding cities. 3) The climbing function curve of the competitiveness of tourism industry in China's urban agglomerations has been verified by practice, and it has universal applicability in the development of urban agglomerations. The function model of climbing law of the competitiveness of tourism industry in urban agglomerations can be used to analyze and predict the future competitiveness of tourism industry in China's urban agglomerations.