Abstract: Importance sampling techniques can effectively enhance the computation efficiency of the Monte-Carlo method in the calculation of structure reliability. How to determine the sampling center is a key problem. When structure performance functions can not be explicitly expressed by random variables and need to be determined by finite element analysis, Neumann series expansion is incorporated into finite element numerical tests in the traditional response surface method. This can speed up the process for searching the design point, which is then used as the sampling center and importance sampling is conducted. Monte-Carlo method is further employed to obtain the failure probability. Numerical examples show the proposed method, the importance sampling Monte-Carlo method based on Neumann expansion response surface techniques, has high computation efficiency and maintains excellent computation accuracy.