In order to meet the demand of developing high precision master gears a nd gear cutters, the influence of belt tightness on the Y7125 grinder’s vibrati on level was studied experimentally. The rule of variation of the Y7125 grinder ’s vibration with the belt tightness was obtained by comparing the vibration di splacement amplitude of key parts of the Y7125 grinder under varied belt tightne ss. Finally the vibration displacement of grinding wheel dresser guide was reduc ed by 5574％, and the vibration displacement of grinding wheel spindle front c over was reduced by 7647％ by optimizing belt tightness of wheel generator. Th e experimental results show that optimization of belt tightness can reduce the v ibration of Y7125 grinders.