Abstract: The heat release rate of the main pump in nuclear power plant continued to rise, it was found that the bearing surface of main pump was abnormal worn through inspection. In order to analysis the causes and the level of the wearing of the bearing surface, the physical properties of the material of the bearing were tested, and the wear degree was analyzed qualitatively by using Archard formula. The results show that the larger the thermal expansion coefficient of the bearing is, the thinner the thickness of the liquid film is, which is easy to cause the damage of the liquid film and is not conducive to the cooling of the bearing. The uneven distribution of the material of bearing is easy to the wear particles produced, and the gas in the liquid film is increased, both of which make that the cavitation phenomenon between the bears more serious and the liquid film is local damaged and the dry friction is happened.