Public library service is an important component of public cultural service system. With the progress and change of public needs, the conflict between public library service supply and demand has been increasingly fierce, bringing new challenge to public library service. It is an innovative method to realize supply-demand equilibrium of public library service and increase public library service efficiency by introducing supply side reform into the field of public library service and starting reform from supply side to demand side. The key of supply side reform of public library service is to define value orientation and position of supplying subject, to rely on sound operation and practical action as basis, to improve resource allocation, to adjust supply structure, to increase supplying capacity of supply subject based on socio-market mechanism, to build a multi-supply mechanism among government, market and society, to improve supporting mechanism of supply side reform, and to force supply-demand balance using supply side reform, so as to realize double implementation of both supply and demand.