Abstract: The column is a weak link that affects the overall stiffness of the machine tool, and its performance directly affects the machining accuracy of the horizontal machining center. Therefore, a multi-objective optimization design method for the stepped rail column of the horizontal machining center is proposed. Firstly, based on Ansys simulation, it was found that the column is the weakest link affecting the static and dynamic performance of the entire machine tool, and the stiffness of the column is the worst when the spindle box is at the top edge of the column. Secondly, select column span, column height difference, screw surface width, and upper guide rail surface width as design variables. Then, using the deformation range in the X and Z directions of the column guide rail surface, first-order natural frequency, and mass as evaluation indicators, a multi-objective genetic algorithm is used to seek the optimal solution. Based on this, sensitivity analysis is used to round and verify the design variables through simulation. Finally, the results showed that the maximum deformation in the Z-direction of the optimized column guide rail surface was reduced by 7.37%, the Z-direction deformation range was reduced by 11.57%, the X-direction deformation range was reduced by 2.41%, and the first-order natural frequency was increased by 1.4%.