Supply chain financing can boost the credit level and ability to make loans of small and medium sized enterprises. The core enterprise has huge stimulating effect to supply chain credit. Supply chain credit and credit multiplier are defined to measure the stimulating effect, and the decision of loan-to-value ratios of a loss aversion bank is analyzed when products are in a newsvendor market which is consisting of a supplier (the core enterprise) and a retailer. Firstly, the optimal loan-to-value ratio of the bank is given. Secondly, the influence of credit multiplier, inventory quantity, the repurchase parameters and loss aversion coefficient on the loan-to-value ratio are analyzed. The results show that the optimal loan-to-value ratio under supply chain financing model is higher,and loan-to-value ratio is positive related to both credit multiplier and the repurchase parameters, and is in negative correlation to both inventory quantity and loss aversion coefficient. Finally, the sensitivity analysis is given to illustrate the conclusions. By defining supply chain credit and credit multiplier, the focus of supply chain financing is transfered from small and medium sized enterprises' credit to supply chain credit.