The welding robot inevitably produces arc force, which affects the welding stability to some extent. In order to solve this problem, 3R welding robot model was built in SolidWorks, the influence of arc force on the welding torch in the welding work was analyzed to reveal its dynamic characteristics in the welding process, to explore the relation between the end welding torch operation stability and welding area arc force. Connecting with the complex working condition, multiple sets of electric arc force with different size, nature and frequency were selected to make simulation, to find the link between the different arc force and the welding torch movement stability. The research results show that the disturbance to the welding torch from the arc force with different size, different properties and different frequencies has certain regularity, especially the change of frequency; when the welding power frequency tends to 20 Hz, the welding torch chattering is unusually intense, resonance phenomenon occurs.It provides reference for preventing unusual resonance of welding torch.