Abstract: Steam generator (SG) is the key component of primary and secondary circuits in pressurized water reactor (PWR) nuclear power plant. Its integrity is very important for the safe operation of PWR nuclear power plant. During operation, the secondary side flow of SG will cause the vibration of the heat transfer tube, which will lead to the collision between the heat transfer tube and the supporting parts, resulting in the fretting wear of heat transfer tube. With the increase of the service life of SG, fretting wear between the heat transfer tube and the supporting parts causes the failure phenomenon of heat transfer tube to increase gradually, leading to the tube wall thinning or even rupture, thus affecting the efficient and safe operation of nuclear power plant. For the fretting wear phenomenon of SG heat transfer tube, the fretting wear behavior of 690TT alloy SG heat transfer tube under high temperature and high pressure water environment through experimental research was simulated in the paper. The fretting wear test system independently developed in China, was used for fretting wear test of tubular and plate friction pairs under high temperature and high pressure water environment. After the test was completed, the wear volume, the three-dimensional morphology of the wear marks and the section profile of the wear parts were analyzed by using the white light interferometer, and the wear coefficient of the 690TT alloy heat transfer tube under high temperature and high pressure water environment was calculated. The effects of the fretting cycle and displacement amplitude on fretting wear damage mechanism and wear performance of 690TT alloy heat transfer tube were systematically studied. The results show that the fretting cycle has little influence on fretting wear behavior and damage mechanism, but it has influence on the evaluation of material wear performance. It is necessary to calculate the exact material wear coefficient by difference method. The displacement amplitude has great influence on the fretting wear behavior and damage mechanism of the heat transfer tube. When the amplitude increases from 20 μm to 150 μm, the wear coefficient increases from 1.014×10^-13 Pa^-1 to 3.653×10^-13 Pa^-1. Under high temperature and high pressure water environment, fretting wear condition is very complicated. A variety of wear mechanisms, including adhesive wear, fatigue wear, stripping wear and oxidation wear, cause fretting wear damage. When the amplitude is small, the main wear mechanism is adhesive wear, and the characteristic region is adhesive wear. When the amplitude increases, the wear mechanism changes to oxidation wear, stripping wear and abrasive wear.