The main content of gear design is the strength design, and the contact strength design of gears is the main heart of the strength design, because the stress and deformation of gears directly affect their safety and service life and concern whether vehicle transmissions work smoothly. Therefore it is necessary to perform a finite element analysis for the gear contact in transmission. Based on the contact characteristic of helical gears, a three-dimensional solid model was established by using the software Pro/E, and the contact stress analysis of gears was carried out by the software ANSYS Workbench. The stress and strain distribution contours of helical gears were obtained , and then the check of strength and rigidity was performed. Thus, it is convenient for designers both to test the strength of gears and to modify the size of gears.