Gears are key rotor components of many machines and are widely used in many engineering fields such as mining machinery, aerospace; transportation and petrochemical etc, and their failure often cause disastrous results. In practical engineering, it is still tedious to assess gears strength and the stress levels of them are very high nowadays. It is well known that the stress analysis is a basic work of age analysis and reliability analysis. Do a finite element analysis (FEA) is necessary before and after the gears have been made. In this paper, a detail analysis is done with FEA, and the stress distribution of gear is consistent with the real distribution. Also the FEA results show that the location of maximum stress is just the failure site of the gear. The analysis results are meaningful for further work such as reliability assessment and optimization design.