To study the spalling law of aviation engine ball bearings,four sets of ball bearings were used to simulate the actual pits or spalling pits by forming different numbers and distribution of pits on the surfaces of the outer races.The spalling tests of prefabricated defective main bearing were carried out on a bearing tester,and atomic emission spectroscopy,laser net fines analysis and ferrography were used to analyze wear particles in the lubricating oil.The results show that the wear particles generated during bearing peeling are mainly fatigue particles,supplemented by severe sliding particles and cutting particles,and oxidation phenomenon is also found.The spherical particles are mainly below 5 μm,a few distributes from 6 μm to 10 μm,barely above 10 μm.There is an increase (sometimes a sharp increase) in the total particles or the number of large-sized particles during the bearing peeling process.The spalling mechanism of aviation engine ball bearings is as follow:fatigue cracks first appear at the edges of prefabricated pits,and then diffuse to the surface or sub-surface of the outer ring raceway to form a peeling zone,which is caused by the poor dynamic lubrication behind the pits.The peeling area continues to expand along the circumference towards both sides,gradually covering the prefabricated pits,forming a large peeling zone and ultimately leading to bearing failure.