Abstract: Taking the data of China’s A-share listed companies in Shanghai and Shenzhen from 2008 to 2019 as a sample, this paper discusses the impact mechanism of customer concentration ratio on bank credit, and examines the moderating role of monetary policy in it. The study finds that there is an inverted U-shaped relationship between customer concentration ratio and bank credit, that is, bank credit will increase first and then decrease with the increase of customer concentration ratio. And this inverted U-shaped relationship is more sensitive during periods of monetary policy tightening. The research has enriched literature on the impact of supply chain relationships on bank credit, providing reference for enterprises to strengthen supply chain relationship management, and providing a basis for understanding the role of monetary policy in corporate financing behavior.