Abstract: The synergism of cavitation erosion and electrochemical corrosion of X65 pipeline steel under different temperature conditions was studied by ultrasonic vibration cavitation erosion test device. The results show that the pure cavitation erosion damage rate reached the maximum at 40 ℃. With the further increase of temperature, the pressure gradient of cavitation was easy to form. The rapid increase of the number of cavitation bubbles enhanced the interaction between cavitation bubbles, and the micro-jets generated by partial cavitation collapse offset each other, which alleviated the mechanical impact of micro-jets on the surface of the steel, resulting in a decrease of the pure cavitation erosion damage rate. The electrochemical corrosion effect was promoted with the increase of temperature. The enhanced corrosion effect aggravated the surface softening of the material and improved the surface roughness, which was conducive to the formation of bubbles, enhanced the damage of the micro-jet to the surface of the material, and the corrosion promoted the cavitation enhanced damage rate increased significantly. In addition, the cavitation process significantly enhanced the oxygen mass transfer on the surface of the material and accelerated the corrosion process of the steel. The synergistic effect of cavitation erosion and corrosion led to the most serious damage at 50 ℃.