Abstract: A method to estimate the failure probability of structures using Legendre orthogonal polynomial approximate method (LPAM) was presented. Based on the numerical approximate theory, the Legendre orthogonal polynomial with higher moments of performance function was used to approximate the probability density function of performance function. The failure probability of structures can be obtained according as computing ecumenical expression of structure reliability analysis. Six most commonly-used theoretical distributions including normal, lognormal, extreme valueⅠ, Gama, exponential and Weibull distributions, were used to verify the approximate characteristic of LPAM. A structure component example was given for illustrative purposes. The result shows that the failure probability of structures using LPAM is agreed well with those obtained by the conventional reliability methods.