Establishing mechanisms to deliver high-quality cultural resources to reach grassroots constitutes both a contemporary responsibility and an area of service innovation for public libraries. Based on existing practical explorations by public libraries in building mechanisms for high-quality cultural resources to reach grassroots, this paper explores the institutional barriers to such direct delivery from four dimensions: resource provision, supply-demand matching, grassroots reception capacity, and cost efficiency. It argues that coordination mechanisms between resource downflow and grassroots endogenous motivation should be improved, with efforts focused on aggregating high-quality resources, leveraging digital and intelligent empowerment, improving multi-dimensional cooperation, improving policy provision, and stimulating endogenized driving, so as to promote the improvement of mechanism reform for high-quality cultural resources to reach grassroots by public libraries.