The three-dimensional helical gear model based on the geometric parameters is created by using software called PROE3.0. The natural characteristics of helical gear are analyzed by using the finite element method. The natural frequency of the helical gear is calculated by the software ANSYS and the principal mode of vibration is discussed. There are four vibration modes, which are circular vibration, torsional vibration, radial vibration and umbrella vibration. The phenomenon of resonance of the helical gear can be avoided by choosing suitable parameters and changing the natural frequency of the helical gear.