The issues of high financing costs and limited access to capital for small and medium-sized firms (SMEs) are becoming more visible, making it critical to investigate alternative solutions. Using centrally administered state-owned enterprise (SOE) groups holding Hushen Ashare listed companies as a research sample from 2009 to 2019, this study investigates the role of national audits in alleviating SMEs’ financing difficulties within their supply chains from a supply chain finance perspective. The results show that national audits can improve state-owned businesses commercial credit support for SMEs in their supply chains. Mechanism testing show that national audits have an impact through three pathways: boosting information transparency, maximizing internal control quality, and raising executives willingness to take risks. According to heterogeneity research, this strengthening impact is more significant in nonindustry finance integrated enterprises, countries with strong rule of law, and highly competitive marketplaces. Based on empirical evidence, this study applies state audit governance theories to supply chain finance and identifies a chain based governance pathway: “audit intervention → SOE credit transmission → SME relief. ” It broadens the explanatory elements of Chinas socialist audit theory inside industrial chain governance scenarios, giving theoretical foundations and empirical evidence for the development of an autonomous audit knowledge system based on Chinese experience and responsive to real world difficulties.