The failure process of hydrostructures concrete is a stochastic process relating to time and space. The durability failure mechanism, durability failure type and durability failure mode were presented. The relation of durability and resisting ability was studied. Based on credibility theory, the method for predicting service-life of hydrostructure concrete was put forward. Through a typical case analysis, the mend measures to improve durability were introduced. The design method for hydrostructure concrete should be controlled by both stress state and durability instead of traditional one.