With the great promotion of ecological civilization construction, public participation in environmental protection has captured growing attentions. Using the data on the website of Beijing Municipal Bureau of Landscape and Forestry, this paper firstly dissects the development process and current situation of the project of Construction and Maintenance for Trees and Green Lands (CMTGL) in Beijing, and then analyzes the public cognition of the project and its impact factors with field survey data. Research results show that public cognition degree of the project is quite low in general. Only 35% of the respondents have some knowledge about it. Community publicity, TV and radio broadcast are the main media for the public to learn about the CMTGL, while few people gain information about it from the Internet. Individual characteristics of the public have impacts on their cognitions on the CMTGL. The paper suggests that the ways to promote the public cognition of CMTGL should vary according to the the differences in people's education level, economic status, types of employer organizations, and awareness of environmental conservation.