The increasing competition in the tourism industry among regions has given risen to questions such as, how to distinguish rivals and how to adopt scientific competition strategies to improve competitiveness of their own tourism products. Solving these would benefit many tourist cities. As same as the natural organism, tourist city is also an organism which has the life cycle, so we can apply ecological theories and methods in exploring the competition relationship among tourist cities. In this study, a competition judgment framework of tourist cities was built using the niche overlap theory and niche situation theory. And there was two parts contained in the judgment framework, firstly, calculating the niche overlap degrees between every two tourist cities by using the niche overlap formula to judge the competition pressure between every two tourist cities, and then calculating each tourist city's niche size by using the calculation formula of niche status and trend theory to judge every tourist city's competitiveness lever. Eleven tourist cities in Zhejiang province were chosen as the research objects and the competition judgment framework was applied to judge the competitive relationships among them. The results showed that, in addition to the niche overlap degree between Quzhou and Zhoushan which was less than 0.5, the niche overlap degree between other every two tourist cities was above 0.5, some even exceeded 0.9, it could be seen that the niche overlap degree between every two tourist cities in Zhejiang province was high, and so the competition pressures were high between each other. Among the eleven tourist cities, the comprehensive tourist niche of Hangzhou hold the first place, it indicated that Hangzhou had the strongest competitiveness and was in the core position in the tourist market of Zhejiang province, and the comprehensive tourist niche of Ningbo and Wenzhou respectively hold the second and third place, the two cities also owned a favorable position in the tourist market. While, due to smaller city scale, weaker economical overall strength, poorer transport accessibility, lower intensive lever of tourism market and so on, the comprehensive tourist niches of Zhoushan, Huzhou, Quzhou were in the bottom three positions, and they had a weaker competitiveness and were in a vulnerable position in the tourist market. On the basis of above analysis, using the niche dislocation, niche expansion and other niche theories, put forward corresponding competitive development strategies which contained niche separation strategy, niche expansion and specialized strategy, coordinated development strategy and so on for each city on the basis of comprehensive consideration of their niche overlap degree and comprehensive tourism niche values.