Aiming at the problem of partial spalling defect of outer ring and fatigue life caused by it of fan gearbox during operation, taking the output shaft end bearing of 5 MW fan gearbox as the research object, the numerical models of flawless bearing and partial spalling defect bearing with different width and size were established. The explicit dynamic analysis of the model was carried out to analyze the stress variation law of the two bearing components caused by the speed and defect size expansion; based on the nominal stress method and damage theory, the fatigue analyses of non defective bearings and defective bearings were carried out, and the damage and fatigue life of bearings were calculated numerically. The results show that with the extension of local spalling defects and the increase of rotating speed, the stress of each component of the two bearings increases, but the service life decreases.