Against the backdrop of data elements being elevated to a national foundational strategic resource, the economic effects of public data openness, a unique institutional innovation in China, are deconstructed. This serves as a crucial lens for explaining the dialectical relationship between an "active government and an effective market" in the digital economy era. Utilizing data on the launch of government data platforms in 217 prefecture-level cities in China, a multi-period difference-in-differences (DID) identification framework was constructed under a quasi-natural experiment setting. The structural reshaping mechanism of public data element sharing on corporate innovation behavior was empirically examined at the causal inference level. It is found that public data openness can promote corporate innovation. From the perspective of institutional constraints, public data openness facilitates corporate innovation by optimizing the business environment and improving government-enterprise relations. From the perspective of factor supply, public data openness promotes corporate innovation through the enhancement of corporate operational capabilities, increased inter-firm exchanges, and reduced R&D uncertainty. The impact of public data openness on corporate innovation is found to be greater in regions with high digital economy policy supply intensity and high social credit, as well as for private enterprises, small enterprises, and strategic emerging industry enterprises. This effect is also observed only in the openness of well-established and high-quality data. Further analysis reveals that public data has a corrective effect on the decision-making behavior of corporate managers, while it exhibits a masking effect on corporate innovation behavior. These findings provide theoretical underpinnings for explaining the institutional advantages of data governance in the process of Chinese modernization and contribute an Eastern wisdom solution to global digital economic development.