Abstract: In the innovation culture system, libraries are the main force in carrying out original innovation in frontier fields, and they are also an important supplier in the technology element markets. Innovative subjects can obtain more tacit knowledge in library cultural exchanges, so as to have better performance in activities such as industrial research and development and technology spillover. This paper uses the patent citation data of urban public libraries and industrial enterprises to conduct an empirical study. The findings show that the knowledge services offered by urban public libraries can play a significant role in promoting the innovation knowledge spillover of industrial enterprises, which is manifested in increasing the number of patent citations of enterprises in their cities. This spillover effect is more pronounced in the eastern region, in large cities, and in large enterprises. The spillover effect of innovative knowledge brought about by the construction of urban public libraries is mainly realized by the following two mechanisms on the one hand, the knowledge agglomeration function of public libraries has promoted the cooperation among industries, universities and research institutions, then the spillover of innovative knowledge is brought about; on the other hand, the construction of public libraries can improve the level of public services and bring about the inflow of human capital, thus realizing the spillover of innovative knowledge. In addition, the development of the Internet has further strengthened the knowledge spillover effect of urban public libraries.

Key words: public libraries, industry-university-research cooperation, patent citations, knowledge spillover