Abstract: The limitations of the TIG welding include low productivity due to low deposition rates, shallow penetration, and inconsistent penetration in the stainless steel plate with 5 mm thickness. An ultrasonic assisted TIG welding equipment with the assistance of high-intensity ultrasonic was researched and developed to increase the welding penetration and improve the welding efficiency. The frequency and the output power of the ultrasonic are respectively adjusted by the input voltages of the control circuit and the main circuit. The output power of the ultrasonic vibration can be continuously adjusted from 0 W to 1 000 W. Experimental results show that the high-intensity ultrasonic has the effect of increasing the weld penetration. Also, the process is simple and easy-controlled compared with other welding methods for increasing penetration. The ultrasonic assisted TIG welding equipment can satisfy the requirements of the design and application.