High water pressure is one of the difficulties of hydraulic tunnel design, which may cause the lining of the tunnel to be damaged. Aiming at solving the problem that the internal force of the horseshoe tunnel is too large, the optimal design of the tunnel, including the gradient thickness of the side arc and the chamfering of the cutting angle, is optimized by combining the advantages of both the Lizheng software and the finite element analysis software, which is considered to be an economical way. Compared with the original design, the results show that the two optimization methods can effectively improve the capacity of the structure, which meets the engineering requirements. Compared with the gradient side of the arc thickness optimization, chamfering to optimize the construction is more economical. The optimal design of the project can provide a reference for other projects.