By considering the difficulty of temperature measurement of meshing was area of gear, a method of obtaining state parameter of working gear by drilling hole and embedding sensor in the hole was proposed. But the distribution of bending stress of gear would be certainly influencd by the hole opening. Aimed at the problem shown, spur gear was taken as an example, the effect of different hole dimensions on bending stress of gear was studied. A three-dimensional (3D) single model of spur gear with different diameter and depth of hole was respectively established by UG software. Based on ANSYS software, a finite element simulation about the model was carried out. The degree of influence of different hole dimensions on bending stress of gear were compared and analyzed. Simulated results show that hole diameter and depth can all largely change stress distribution of gear, among which, hole depth accelerates the variation of the largest bending stress of gear tooth more acutely.