Abstract: For the commonly used steel Q355B of construction machinery, through the arc welding robot MAG welding, the welding current is controlled at 280 to 400A, and process test research under different welding parameters is performed. The test results show that as the current increases its welding joint performance, there is no significant attenuation. The tensile strength, yield strength, elongation after fracture, bending performance, impact performance, and hardness performance of welded joint specimens all meet the standard requirements, and their performance can reach or exceed the level of the base metal. Welding joints have optimal performance when the current is controlled at 350A. At the same time, compared to when the welding current is small, as the welding increases to above 380A, the efficiency can be improved by about 20%, which is used to guide actual production needs.