The records of mainstream media are ideal materials for studying the popular needs of public libraries. A study of mainstream media excavation in the past 20 years shows that popular demand for public library is mainly reflected in life needs, learning need, emotional and leisure needs. The content of popular demand is analyzed in terms of collection, space, personnel and service dimensions, and the characteristics of popular demand for public library as public, living and alternative are proposed. The evolution trend of popular demand for public library is analyzed in four aspects: public space, public value, public culture and public service. Finally, the author discusses the application of popular demand theory in the 14th Five-Year Plan and the future development of public libraries.