Abstract: An arch dam was stochastically simulated by using Ansys 5.7 stochastic finite element program considering the main loads of a dam and parameters of the materials. The statistical values of the arch dam's stochastic variable and the sensitivity of the stochastic variable to functional function were calculated. And the probabilistic density function of the stochastic variable as gained by the maximum entropy method. Then the distribution of reliability index of the dam as calculated by using numerical integrator.