Gears are widely used in many engineering fields such as mining machinery, aerospace, transportation and petrochemical and are common and important parts for engineering, but for some gears it is still tedious to build the 3D models and assess their reliability. It is important for a gear to do reliability assessment, especially for some gear that under complex load conditions. In order to improve the reliability and stabilization, a gear assessment method is introduced and an example is given, and the example shows that do reliability assessment is useful and effective.