Abstract: Taking a deep groove ball bearing as the research object, a calculating model is established by mechanical analysis, which can analyze the contact stress between rollers and raceways, as well as the axis orbit by considering the rollers' error. Influence of rollers' error on the contact stress of the raceways and the axis orbit is numerically analyzed using a calculating example. The variation curves of maximum contact stress, average stress and axis orbit are also plotted and explained.