Abstract: The failure reason of 3506/355.6/YA-1 double-row cone roller bearing was studied by fracture surface analysis, trace comparison, hardness testing, and microstructure examination. The results show that the failure of the bearing has nothing to do with the material and heat treatment process it had experienced. It is found that one of the rollers had been reversely installed into the inner ring of the bearing, causing bearing failure in advance. There existed excessive contact stress at the contacting zone between the side face of the roller big end and inner ring raceway, resulting in circumferential crack on the inner ring and eventually making the bearing abnormal.