In the circumstance that market demand is uncertain, it studies the decision-making problem of supply chain financial system consisting of the single supplier, a capital constraint retailer and a bank. Considering the mode of external financing, we obtain the optimal order decision of the capital constraint retailer, the optimal financing rate and the optimal wholesale price of the supplier and analyze the effects of owned capitals of retailer on the optimized decision-making of supply chain financial system. At last, it demonstrates the effectiveness of conclusion by numerical examples.