Buoyancy tank and back tie rod are effective measures to improve the torsional resistance of miter gate of medium and low head ship lock. There is less research work considering both pontoon and back tie prestress. Based on the miter gate of a ship lock under construction in Jiangsu Province, a finite element model of miter gate space thin-walled structure is established in this paper. The torsion resistance of miter gates with different pontoons is calculated and compared, and a more reasonable pontoon setting scheme is proposed. On this basis, the torsion resistance of miter gate with different arrangement of back tie rod is studied, and an improved optimization model of back tie rod prestress is proposed, which can improve the overall anti-torsional ability of the gate after the prestress is applied. The research results show that the combined torsion resistance scheme of miter gate with U-shaped pontoon and prestressed back tie rod proposed in this paper can effectively improve the overall torsion resistance of the gate. The research methods and results can provide a reference for the design of miter gate of medium and low head ship lock.