Abstract: The bolt group force analysis of rectangular explosion-proof tank shows that the bolt group’s force is not uniform and the loading curve is inverted "V" shape while the layout is uniform. To improve the connection security of the bolt group of explosion-proof tank, a method for layout optimization of bolt group is proposed in the paper. Based on the principle that the bolt layout density is proportional to strain values of the joint , the force of the bolt group is simulated after analyzing the bolt spacing and the axial force. And then the bolt spacing is optimized by MATLAB optimization program, and the new bolt layout is obtained. The loading curve of the new layout bolt group is flat, The research results show that with the optimization method , the load of the bolt group is reduced and uniform, and the reliability of the bolt connection is greatly improved.