The fretting wear behaviors of TC4 titanium alloy under different displacement amplitudes in air, pure water and the artificial seawater of 3.5% NaCl were studied by SRV-IV fretting wear test rig. Scanning electron microscopy and laser scanning confocal microscopy were used to characterize the surface morphology, wear volume and wear profile of the wear scar. Fretting wear mechanism of the titanium alloy in different environmental media was analyzed. The results show that the friction coefficient increases first and then decreases with the increase of the displacement amplitude, while the wear volume increases. Under the dry friction condition, the friction coefficient is higher and unstable, and the wear volume is smaller. The wear mechanism is mainly abrasive wear, adhesive wear and oxidative wear. Compared with dry friction, the friction coefficient in the aqueous water is lower, the wear volume is significantly increased, and the friction coefficient in the artificial seawater is lower and more stable, and the wear profile is deeper, indicating that there is a "positive" interaction between corrosion and wear. The fretting wear mechanism of TC4 alloy in pure water is mainly fatigue wear and abrasive wear; while the fretting wear mechanism in artificial seawater is mainly abrasive wear and corrosion wear. © 2020, Science Press. All right reserved.