The spread of COVID-19 epidemic has worsened the situation of private enterprises which have difficulties in financing. A large number of enterprises have generally encountered a cash flow crisis, which arouses strong social concern. In response to this emergency, the Chinese government issued a series of financial support policies for private enterprises to tide the difficulties. It can be seen that, on the one hand, the government is still playing a vital role in helping enterprises under China’s current economic system, especially in extraordinary times; on the other hand, the financing security of the private economy is still fragile. The lack of market-based financing channels is still a hidden danger for enterprises to ensure liquidity security, which severely reduces the ability of private enterprises to resist risks. Therefore, how to give full play to the role of the government and help private enterprises solve the financing dilemma has become an important issue that needs to be considered, and is also a hot research topic with Chinese characteristics.However, the existing literature on government support is mostly focused on traditional ways such as subsidies and tax incentives, and has found that these government interventions have not achieved effective results, leading to a lot of rent-seeking behavior and zombie enterprise problems. Still, there is an apparent lack of understanding of the procurement behavior of emerging government background customers. In reality, the government can support private enterprises by purchasing the products of private enterprises through public bidding, and it is more helpful to improve the operating ability of enterprises than the direct government subsidy. Therefore, whether the impact of government support can affect private enterprises through supply chain should become a new research perspective to enrich the study of government interventions.Based on the customer information of listed companies from 2007 to 2015, this paper indicates that major government background customers can effectively reduce the level of corporate financing constraints, and this relationship is more pronounced in the sample of high industry competition, poor economic development areas, weak social credit levels, and periods of higher economic uncertainty. At the same time, this paper also explores the influence path of this relationship and finds that the existence of major government background customers can effectively reduce the default risk of enterprises, thus improve market cognition, and then affect the degree of financing constraints. Furthermore, this paper confirms that the mitigation effect of major government background customers on corporate financing constraints will directly increase the business credit and bank loan of enterprises in the next year and extend the repayment period.The main contributions of this paper are embodied in: Firstly, it studies the influence of major government background customers on corporate financing constraints under China’s institutional conditions from the perspective of supply chain. The combination of macro policies with the response of the micro-market provides a new view for the research on government procurement policies. Secondly, it explores the mechanism for major government background customers to ease the financing constraints of private enterprises. In particular, it verifies how the internal and external environment of enterprises can promote the decisive role of major government background customers from the perspectives of enterprise risk, social trust, and economic uncertainty. Moreover, through the path of default risk, this paper reveals how the existence of major government background customers affects the financing constraints of enterprises, which is an essential supplement to the research literature of supply chain. Finally, the research findings of this article also have essential enlightenment for investors to interpret the information content of government-backed procurement obtained by listed companies, and reveal the impact mechanism of macroeconomic policies on third parties in the market.