In order to achieve high efficiency and high quality friction stir welding of complex-structured aluminum alloy products forming， the research on flexible welding systems was carried out based on the combination of KUKA heavy duty robot and new friction stir welding technology. Through self-developing multifunctional friction stir welding host unit and test equipment， the robot flexible welding dedicated control system was developed to realize integration control. Based on this research， the research on microstructure and properties of the joint in the plate welding test piece and the friction stir welding test verification of the space curve trajectory were carried out. The results show that the heavy-duty robot friction stir welding system can stably weld 6 mm thick 2219 C10S aluminum alloy plate test piece and 3 mm thick S-shaped space curve welding test piece. When the stir head rotation speed n is 800 r/min， the welding speed v is 200 mm/min， the mechanical properties of the test piece joint such as tensile strength and elongation are good. Ultrasonic phased array and X-ray inspection are carried out on the welding seam of the sample， and no excessive defects such as holes and cracks are found in the weld， which verified the applicability of the robot friction stir welding system and process method.