Advancing digital governance is a key direction in China’s government governance reform, with the “National Smart City Pilot Program” representing an important event to enhance urban digital governance capabilities in recent years. This paper leverages data from the fourth, fifth, and sixth national evaluation and grading of public libraries at or above county level across 57 eastern Chinese cities. Utilizing the difference-in-difference (DID) method, we empirically examine whether the smart city pilot policy, as a form of digital governance, can improve the development level of public libraries. Findings indicate that pilot policies significantly facilitated the upgrading of second-tier libraries to first-tier status, yet exerted minimal effects on third-tier library quantities. This reveals a “the strong get stronger, the ordinary remain ordinary” dynamic in policy implementation. This research contributes to the literature on evaluating digital governance policy effectiveness and provides empirical foundations and policy insights for refining digital governance policies.