Abstract: Differential sliding friction is one of the main friction heat sources of high-speed ball bearings. The differential sliding state of contact area was analyzed based on the quasi-static calculations of high-speed ball bearings. Combined with the rheological properties of lubricants in elastohydrodynamic lubrication condition, the differential sliding velocity, slide-to-roll ratio and the friction coefficient distribution in the contact area are determined, and the differential sliding friction heat is calculated. The influence of the bearing speed, load, groove curvature coefficient and initial contact angle on the differential sliding state was analyzed, and the variation of the differential sliding friction heat with speed, load, groove curvature coefficient and initial contact angle was obtained, which lay the foundation for the study on thermal characteristics and the optimization of structural parameters of high-speed bearings.