For the probability reliability analysis of gravity dams，it is difficult to obtain the parameters in real time，and the extreme state equation is highly non-linear or even not explicitly expressed.In this study，based on the attenuation function to obtain the statistical information of post-service gravity parameters of gravity dam.The Kriging model is combined with the strong-fitting ability，the Kriging model of the limit state of gravity dam is established，and the verification method is given.According to the geometric definition of reliable index，the gravity dam reliability index optimization calculation method is developed.Through case studies，this method effectively considers the impact of service on the reliability of gravity dams，and it is well adapted to the highly complex engineering characteristics of gravity dams.It can provide a more realistic and in-depth analysis of the operational reliability of gravity dams.