Abstract: In order to predict the failure tocation and service life of gears in combine harvester chassis gearbox, the three-dimensional finite element model of input gears was established by using SolidWorks and the external load was added according to actual working situations. A surface contact mechanical model was applied to analyze the gears mechanical characteristics, and to calculate Von Mises stress, displacement and strain distribution on the teeth. The maximum Von Mises stress was about 394.16 MPa, which was less than the yield limit. Root of the teeth would not rapture. The probability of gear failure was predicted by the Weibull distribution, and the distribution curve was created based on the S-N curve defined inthe Simulation module. It predicted that the failure probability was about 93.96% when the gears worked 500 hours. The fatigue property experiment was carried out in the self-made gearbox fatigue test bed. The results indicated that serious pitting appeared on the surface of the teeth when the working time was over 500 hours. The input driving gear was completely failure, which basically coincided with the theory analysis results.