In order to study the stress of main shaft under the external force, three-dimensional parametric modeling of the cutting spindle of a certain type boring machine was carried out by using the finite element modeling software Design Model. Then, the finite element static analysis was made by Work bench, and stress distribution and deformation of cutting spindle in the case of external stress were obtained. The result also showed that influence of torque to the spindle, which provided theoretical basis for the structural optimization and the improvement of the process parameters.