Abstract: For the annular weld of large valves, a multi-layer and multi-channel path planning method based on groove size, welding pass, welding gun collision verification and welding gun angle correction is established by using the path planning strategy of contour arc filling. By fitting the groove filling weld into fan-shaped weld, isosceles arc trapezoidal weld and fan ring weld, the position, angle and swing amplitude of the welding torch of each weld are calculated. The interference of the weld is judged, and the deflection angle of the welding torch is determined. The off-line programming of robot valve variable posture welding is realized, and the robot interference collision in the welding process is avoided. Finally, the welding of large butterfly valve was realized. The surface of the welded joint was flat without cracks and fusion defects. After ultrasonic testing, there was no internal defect, and the qualified rate of the weld was 100%. The microstructure of the welded joint is composed of pearlite and ferrite, and the grain is fine and uniform. The tensile strength is 536 MPa, the yield strength is 468 MPa, the elongation is 14 %, and the impact energy at 0 ℃ is 54 J.