Abstract: In engineering structural design, the accuracy and efficiency of the reliability-based design optimization (RBDO) are the key issues. A decoupled method based on an integrating approach is proposed for RBDO. In the proposed method, the approximated function for decoupling in the current iteration is a weighted integration of the failure probability functions (FPFs) obtained in previous iterations. After the original reliability-based optimization problem is decoupled, it is solved within the sequence approximation optimization framework. Compared to the traditional approach that only uses the currently built FPF for decoupling, the proposed approach utilizes all the information generated in previous iterations to solve the problem. It results in a more reasonable and accurate approximation of the FPF, leading to the reduction of the number of iterations and the computational cost. Examples of roof truss and ten-bar structure are given to validate the efficiency and robustness of the proposed method.