In recent years, the issue of capital constraints faced by vehicle manufacturers has emerged as a key obstacle to the new quality productive forces development of the vehicle industry. To address this challenge, research on financing strategies for the new energy vehicles supply chain aims to effectively alleviate these capital constraints for vehicle manufacturers. For a supply chain structure comprising vehicle manufacturers and battery manufacturers, decision optimization models were constructed under three scenarios: vehicle manufacturers with no capital constraints, vehicle manufacturers opting for bank loans under capital constraints, and vehicle manufacturers choosing internal supply chain financing under capital constraints. These models were solved and analyzed using Stackelberg game theory. Furthermore, case analysis methods were employed to verify the model results, and corresponding management suggestions were provided for enterprises. The research findings indicate that, under the bank loan model, interest rates positively correlate with the sales prices of new energy vehicles, while negatively correlating with the profits of vehicle manufacturers and battery manufacturers. Under the internal supply chain financing model, interest rates positively correlate with battery research and development levels, vehicle sales prices, and the profits of vehicle manufacturers, while negatively affecting the profits of battery manufacturers. When interest rates are equivalent, the profits of vehicle manufacturers and battery manufacturers are consistently higher under the internal supply chain financing model. Thus, vehicle manufacturers should actively seek internal supply chain financing with battery manufacturers to resolve capital constraints.