Using the launch of public data opening platforms by local governments as a quasi-natural experiment and selecting data from Chinese A-share listed companies in Shanghai and Shenzhen from 2007 to 2023, this study empirically examines the impact of public data opening on corporate debt financing costs. The results show that public data opening can significantly reduce corporate debt financing costs. Mechanism tests indicate that public data opening can effectively reduce corporate debt financing costs by alleviating information asymmetry and improving corporate operating stability. Heterogeneity analysis demonstrates that this effect is more significant for private enterprises, firms with lower market positions, and firms located in regions with lower levels of e-commerce development. In addition, public data opening can increase the overall debt financing scale and short-term debt financing scale.