Abstract: An improved method is proposed for the analysis of failure path reliability in a concrete gravity dam under non-stationary ground motion processes. Firstly, the relation between failure probability of failure path and elements in failure path was given. Then, the demand variables were replaced by dummy variables in order to simplify the process of solving the gradient in the first-order second-moment method. And the required parameters were obtained through a deducing pseudo excitation method and some other formulas. Finally, an algorithm was proposed to search the minimal reliability failure path. The calculation result shows that this method has high practicability and a fast convergence speed.