Back tie rods are essential components of miter gate.In this paper,computing methods of non-prestressed back tie rods are compared to that of prestressed back tie rods in miter gate,and improvement measures of the non-prestressed back tie rods are given.By the finite element software,torsional stiffness of different structure types of miter gates is analyzed.The relationships of the control parameters of the gate deformation are pointed out,and the huge role prestressed back tie rods play in promoting the torsional stiffness and reducing the gate head drooping is confirmed.