The invention discloses a welding method for duplex stainless steel process pipes. S22053 duplex stainless steel is adopted. The method comprises steps as follows: 1) V-shaped butt-welds are adopted; 2) argon tungsten arc welding is adopted for backing welding and second pass welding, shielding gas introduced into a welding gun is pure argon or mixed gas of argon and ammonia, the volume of the argon in the mixed gas is larger than 95%, the flow of the shielding gas ranges from 10 L/min to 15 L/min, and line energy parameters are controlled; the interlayer temperature is controlled to be lower than 250 DEG C until backing welding and second pass welding are completed; 3) a pipe with the wall thickness smaller than or equal to 10 mm is fully welded through gas-shielded arc welding with the pure argon; for a pipe with the wall thickness ranging from 10 mm to 32 mm, a weld layer is filled with manual arc welding and adopts cosmetic welding, and the interlayer temperature is controlled to be lower than 200 DEG C until full welding is realized; 4) after welding is completed, pickling passivation treatment is performed. With the method, the welding quality and efficiency can be improved through argon and arc combined welding, and the cost can be reduced.