Abstract: The purpose of this paper is to study the reliability calculation and reliability sensitivity analysis of gear bending fatigue under uncertain parameters. Under the condition of stress ratio of 0.04, the S-N curve and P-S-N curve of gear under different reliability were established. Considering the uncertainty factors, Monte Carlo method was used to simulate the reliability of gear bending fatigue based on the stress-strength interference model, and the results were good. Combined with the reliability simulation results and the sensitivity calculation model, the mean sensitivity and variance sensitivity of each random parameter under different reliability after dimensionless removal were obtained. The results show that the positive and negative correlations of each mean sensitivity exist together and the influence is gentle under different reliability. In variance sensitivity, except for parameter Y_F, which is negative at all reliability degrees and has gentle influence, the other six parameters are positive at all reliability degrees and have severe influence.