The invention discloses a 
resistor heat source-assisted composite double-shaft needle-free 
friction stir welding method. The method comprises the steps that stirring friction heads are adopted as electrodes of a 
resistor heat source, high-density currents are provided for the interior of a to-be-welded workpiece through a direct-
current switch power supply, and the 
resistor-assisted heat source is provided for the stirring heads in the 
friction stir welding process; the stirring heads rotating at a high speed are inserted into the two sides of a joint, and upsetting pressure is exerted to 
metal at the joint through a shaft shoulder, so that the 
metal material at the joint is softened; the 
metal structure at the joint achieves a plasticizing state under the stirring effect through the stirring heads rotating at the high speed, and meanwhile micro-
forging treatment is conducted on the plasticized metal by adopting an 
ultrasonic vibration exciter, so that metal structure crystalline grains at the joint are refined; the stirring heads do feeding motion in the direction of the joint, a cavity formed after a stirring needle moves is continuously filled with the plasticized metal under the stirring and extruding effect of the stirring heads, and the plasticized metal is gradually cooled and solidified to form a final 
welding joint. According to the method, the life of the stirring heads is prolonged, the 
welding thickness is increased, the 
welding speed is increased, and welding defects are reduced.