Based on the geometrical principle, the machine tool kinematics principle and the actual working conditions of gear machined by the computer numberical control (CNC) forming grinding machine, the simplified model of grinding force was established. The relation between the grinding force and the wheel feed rate was calculated by the grinding force of empirical formula, and the trend of changing of the grinding force in different wheel feed rate was analyzed. The vibration signal was collected by the built vibration test platform, the changing of the vibration signal in different feed rate was analyzed by using Fast Fourier Transform (FFT) to get the relations among the wheel feed rate, the grinding force and the vibration characteristics. The reference can be provided to improving the grinding quality of the tooth surface.