Abstract: Quantitative assessment of public environmental concern has always relied on the traditional method-questionnaire. Under the background of big data, this paper put forward the theoretical basis and method to reflect public environmental concern using web searching behavior. After deeply analyzing the connotation of public environmental concern, this paper put forward 4 levels of connotation in logical relations. Using Baidu index data of environmental key words at various levels, this paper made an empirical analysis of Beijing's public environmental concern index and its influencing factors. It was found that public environmental concern in China, including Beijing, had declined to a certain extent in recent years, and public environmental concern had been significantly affected by economic development and the level of environmental pollution. This enlightens our country about improving the level of public environmental concern. We should pay attention to the use of regional advantages. In the new situation, we need innovative ideas and methods to promote the public's environmental participation in China.