Traditional electric power credit research and application are mainly based on negative evaluation such as electricity behavior, payment behavior dishonesty, lacking of positive evaluation and incentive application, only applied to customer management and electricity risk prevention, no cross border application in society.Firstly, the power credit indices of high voltage enterprise customers are concentrated on two aspects: trustworthy ability and trustworthy behavior. A comprehensive evaluation index system for power credit of high voltage enterprise customers based on big data is designed, which includes six evaluation dimensions: power consumption value, power grid interaction value, payment behavior,power consumption behavior, service interaction behavior and power market transaction integrity. Secondly, the process of calculating, revising the credit rating and credit score of electric power is designed. Taking nearly 290 thousand high voltage enterprise customers of a provincial power grid as examples,the scientificity and standardization of the established method are proved. Finally,based on the electric power credit rating, the differentiated reward and punishment measures are designed, which can effectively guard against internal risks, tap high quality customers and realize the export of electric power credit valuel.