The concentration and contagion of financial risks is a hidden crisis that may lead to systemic financial risks. How to identify and prevent the financial risk contagion of micro firms is of great significance to prevent and resolve the systemic financial risk. Based on the listed companies from 2010 to 2020, this paper constructs the “customer supplier year” sample, and investigates the contagion effect of core customer financial risk on supplier enterprise and the strategies suppliers will adopt. The research results show that:(1) the core customers have a financial risk contagion effect on suppliers. And supplier enterprises can effectively deal with the risk infection of core customers through “corporate governance improvement ” and “information quality improvement ”. (2) The identification of action path shows that “benefit linkage effect” and “resource linkage effect” are underlying mechanisms. (3)The heterogeneity test finds that when the enterprise environment is more dynamic and the supply chain network is more volatile, the contagion effect is more obvious, and the supplier's strategies to deal with the financial risk contagion of core customers through the “corporate governance improvement ” and “information quality improvement ” are more obvious.