As an enterprise property, the customer relationship shows kind of uncertainty, which results in customer risk and even threats the development of enterprise. Aiming at providing a theoretical basis for the effective customer risk management, firstly, the customer relationship is divided into three types: contractual context, semi-contractual context and non-contractual context, according to the degree of strength of contract binding between enterprise and customer and analysed customer behavior features; secondly, the customer risk system which is composed of the risk of customer acquisition, the risk of customer retention and the risk of termination is built according to the customer life cycle and its definition, origin and result are also discussed. Furthermore, the characteristics of relationship between three contexts and three types of customer risk is explored in line with “transactional relationship type-transactional relationship binding-customer behavior-customer risk”.