Abstract: With the large-scale integration of new energy, the demand for refined regulation of grid voltage in power system is increasing, which makes the action of on-load tap-changer more frequent, and the electrical wear of its contacts is serious and the failure rate is increasing year by year. In order to explore the electrical wear of the switch contacts of the on-load tap-changer in insulating oil, the arc characteristics generated during the sliding process of the on-load tap-changer are studied. Based on the theory of fluid dynamics, the arc plasma simulation analysis model of the on-load tap-changer is established, and the temperature distribution of the arc and the temperature distribution characteristics of the contact surface of the on-load tap-changer are simulated. The current-carrying friction and wear test platform of the on-load tap-changer is built in the laboratory, and the arc simulation model between the contacts is tested and verified. The results show that the surface temperature of the contact increases slowly with time and decreases with the increase of sliding speed before arcing. During the arcing process, the arc temperature increases extremely, the current increases, the arc energy increases, the arc temperature and the contact surface temperature increase. Before the sliding velocity of 55 mm/s, the arc temperature increases with the increase of the sliding speed. When the sliding speed is between 55 mm/s and 100 mm/s, the arc temperature decreases first and then increases, and the arc energy reaches the minimum when the sliding speed is 90 mm/s. The discovery can provide reference for the optimal design of the contact mechanism.