Abstract: To explore the collusion and loan fraud behavior of low-carbon supply chain enterprises with financial constraints in the context of green finance, a tripartite game model was constructed between banks, core enterprises, and small and medium-sized enterprises. The key influencing factors of core enterprises and small and medium-sized enterprises colluding to defraud green loans from banks in low-carbon supply chains were analyzed, and the impact of bank regulatory costs, regulatory success rates, and collusion punishment levels on supply chain enterprise collusion decisions and bank regulatory strategies was analyzed. Research has found that the “ease of operation” and “concealment” of collusion among enterprises, as well as the regulatory costs and punishment severity imposed by banks on collusion, are key factors influencing collusion behavior among enterprises in the low-carbon supply chain; With the continuous increase in the cost of banking supervision, the motivation and intensity of banking supervision have weakened, and the probability of collusion among enterprises continues to increase; When the green lending rate of a bank is relatively high, that is, when the difference between the bank's green lending rate and the ordinary lending rate becomes smaller and smaller, the probability of collusion among enterprises increases; By investing in and constructing emerging technologies, banks can form efficient regulatory capabilities (i.e., higher regulatory success rates), and by strengthening the punishment for corporate collusion, they can effectively deter corporate collusion and reduce the motivation and probability of collusion.