The invention relates to an angular contact ball bearing. The angular contact ball bearing comprises an inner ring, a middle ring, an outer ring, a sealing cover, a plurality of steel balls and a retainer, wherein the middle ring is arranged outside the inner ring; the outer ring is sleeved outside the middle ring; a double-line internal raceway is formed between the inner ring and the middle ring; a double-line external raceway is formed between the middle ring and the outer ring; the plurality of steel balls are in angular contact distribution in the double-line internal raceway and the double-line external raceway through the retainer; and two circles of sealing covers are arranged on the double-line internal raceway and the double-line external raceway respectively. In the angular contact ball bearing, a combined bearing is adopted to replace two double-line ball bearings so that an engine cooling system of a large bus in China is changed to three-stage speed change from two-stage speed change. The bearing flexibly rotates, is uniformly stressed, makes a main machine run at low speed, medium speed or high speed, reaches the advanced level in the world, meets the requirements of speed change in auto industry, and has the characteristics of low cost, long service life, high rotation speed, light speed change, low noise and the like.