Abstract: Based on visual real-time sensor,a method to control the weld width was proposed to solve the problems of weld appearance in the welding process of aluminum alloy plate with constant welding parameters,which include the weld width broadening and bead subsidence due to the strong heat accumulation effect.The width was controlled by the heat input,which was realized by changing the duty cycle of the double pulses.The rapid prototype system with close loop control was established based on Labview visual sensor and xPC target real-time object environment.The results show that the system of visual sensor and rapid prototype have quick response performance.The heat input can be effectively reduced by regulating the procedure of the cyclical double pulses,the weld width is well controlled,and weld appearance is good.