In order to explore the response mechanism of PM2.5 concentration in ecotourism cities under the change of tourism activity intensity, the multifractal characteristics of PM2.5 and tourist population in Zhangjiajie City, China are analyzed respetively by using multifractal detrended fluctuation analysis method. The results show that the evolution of PM2.5 and tourist population has nonlinear and complex multifractal characteristics, and the multifractal characteristics of PM2.5 was stronger than that of tourists population. Furthermore, the cross-correlation between PM2.5 and tourism population is studied by using multifractal detrended cross-correlation analysis method. Itprimes found that not only there are multifractal characteristics with long-term sustainability between them, but also the multifractal characteristics of their correlation are obviously affected by the intensity of tourism activities, which shows that the multifractal characteristics in tourism peak season is stronger than that in slack tourism season. Finally, the backward trajectory model is used to analyze the spatial source of PM2.5 pollutants in Zhangjiajie during peak and slack tourism seasons. The results show that the PM2.5 pollutants in Zhangjiajie are mainly due to the local emissions, which indicates that tourism activity is the main influencing factors of PM2.5 in Zhangjiajie City.