Abstract: In order to improve the reliability and economy of repair process of hydraulic support, the application effect of ultrasonic plasma arc welding was numerically simulated and experimentally studied.According to welding gun structure and welding parameters of the designed ultrasonic plasma arc welding system, the finite element model of ultrasonic field was established, and the velocity field, arc density field and sound pressure field of plasma gas were solved based on COMSOL.The microhardness, residual stress and impact toughness of the repaired hydraulic support samples were tested.The results showed that ultrasonic could increase the arc pressure by more than 20% under the same conditions, significantly enhance the current density within 4 mm arc diameter, and effectively reduce the range of heat affected zone and residual stress.The plasma gas velocity and arc density appeared an approximately opposite trend in the area near the support weld, and the second-order characteristic frequency vibration source could produce a standing wave near the electrode.Compared with the base metal, the average hardness and room temperature impact energy of the repaired support welds increased by 45% and 45.8% respectively.Highlights:(1)According to the structural characteristics of the ultrasonic plasma arc welding system, the matching finite element model of ultrasonic field was established.The velocity field, arc density field and acoustic pressure field of plasma gas in the model were solved based on COMSOL.(2)In order to verify the improvement effect of ultrasonic on comprehensive mechanical properties, mechanical properties of repaired specimens were tested and analyzed, including microhardness, residual stress and impact toughness.