Taking the cutting torque shaft of MG2×250/1200-WD shearer as the research object, the multi-parameter optimization of four key structural parameters of U-shaped unloading groove, such as groove bottom diameter, groove bottom arc radius, polished rod diameter and axial position of unloading groove, was carried out by using finite element simulation and orthogonal test. A three-dimensional geometric model of the torque shaft was established and reasonable boundary conditions were applied. Nine sets of test schemes were designed based on the L9 orthogonal table. The static simulation of each scheme was carried out by Inventor finite element analysis software, and the maximum shear stress at the unloading groove was obtained. The range analysis method was used to evaluate the primary and secondary effects of various factors on the maximum shear stress. The theoretical optimal parameter combination was determined based on the main effect trend of each factor, and the combination was verified by supplementary simulation. The results show that this method can effectively give the optimal design parameters of the U-shaped unloading groove of the torque shaft, which can provide a reference for the structural design of similar torque shafts.