On the single factor model of CAPM, this research builds a total risk optimal model, where the objective is to minimize the total risk of loan portfolio under constrain of setting expect return. we build a portfolio loan total risk control model. The character and innovation of the model is firstly the total risk optimal model analyzes the affect of the systematic and unsystematic risk on the commercial bank loan portfolio, so the description of the financial assets portfolio will be solved. Secondly, the aim for apart the systematic and unsystematic risk from the total risk is to eliminate the unsystematic risk by adding loans from different industry and area, which will satisfy the principle of safety of commercial bank. Thirdly, we set the expect return, it can effectively apart the less return loan portfolio, so the loan return will be enlarge since the present loan of commercial bank won't be increased, which will principle of profitable of commercial bank.