This product contains a highly integrated friction stir welding head, which is designed with equal strength structure theory to effectively solve the welding deformation problem of workpieces at different heights; the welding head ensures the stability of welding accuracy; it is provided with the normal following and small arc optimization functions to keep the friction stir welding head moving consistently in the welding path and avoid welding defects; the standard constant pressure function effectively reduces welding defects caused by inconsistency between the incoming material error and clamping/positioning error and the ideal model.