Gear form grinding is an efficient finish machining method for the gears with hard face. There are many factors which have an influence on tooth error in grinding process. In addition to the form error of form grinding wheel, the radial feed depth of grinding wheel has large impact on the tooth error. Based on the principle of gear form grinding, the influence of wheel feed depth on tooth error is analyzed theoretically. The magnitude of error is also analyzed quantitatively according to the simulation result obtained by means of tooth error analysis module, which is developed based on VC + +6.0 software analysis. The research result has a certain reference value for preparing CNC form grinding process and setting machine tool properly.