Library policy is an important institutional guarantee to promote the high-quality development of librarianship and support the construction of a culturally strong country.It is important to explore the factors,processes and characteristics of library policy evolution so as to provide references for the improvement of policy practice.The article selects 186 important policy texts issued at the national level from 1949 to 2023 as the research objects,and constructs a library policy evolution factor model with the help of the grounded theory method from four aspects,namely,policy environment,policy subjects,policy tools and policy goals,and divides the process into the preliminary exploration period(1949-1977),the reform and development period(1978-2011),the innovation and prosperity period(2012-present).It is found that its evolution features include four aspects:the gradual opening up and improvement of the policy environment,the shift of policy subjects to coordinated participation,the equilibrium of policy instruments,and the systematic promotion of policy objectives.Accordingly,recommendations are made to strengthen the top-level design of policies,improve the mechanism of synergy among policy subjects,optimize the structure of the use of policy tools,and promote the assessment of the effectiveness of policy objectives.