This paper analyzes and interprets the main policies and laws in the fields of ecological environmental protection and culture in China in the past 20 years, and explains that participating in the construction of ecological civilization is the social responsibility entrusted to library in the new era of socialism with Chinese characteristics. The legal informational, educational functions, and cultural functions of library and the "Third Space" function determine that libraries have the obligation and rights to participate in the construction of ecological civilization as the main body of responsibility. The construction of ecological civilization has multiple subjects, which requires the libraries to participate in it. Library can give full play to the functions of providing environmental protection information resources, carrying out environmental protection publicity and education, disseminating environmental protection knowledge and information, building ecological culture, bringing together environmental protection forces, exchanging ecological ideas, and so on.