Abstract: In order to solve the complicated calculating indexes and difficulty to draw the best results of the retaining walls design. The smallest cross-section objective function of the gravity retaining wall is established which can meet the stability and the requirements of the bearing capacity of foundation, get the non-linear mathematical optimization model and a domes-tic mathematical optimization software lstOpt is used to solve. This method avoids the cumbersome process of the trial calculation and a reasonable cross-section of economic size could get, and has been successfully used in Zhong Wu gas line along the protection of hydraulic engineering.