The invention relates to a welding method for 12Cr1MoV and 07Cr19Ni 11Ti dissimilar steel. In the prior art, austenite and pearlitic steel are mostly welded by adopting constantan welding wires, so that the cost is higher, weld joints are deformed and cracked, and welding in the prior art is not suitable for batch production. The dissimilar steel comprises dissimilar steel A (1) and dissimilar steel B (2), the butt gap b of the dissimilar steel A and the dissimilar steel B is 2.0 mm-3.0 mm, the groove angle a is 30 degrees-35 degrees, the truncated edge p is 1.5 mm-2.0 mm, the thickness delta of a pipe is 5 mm, a TGS-347 welding wire is adopted, the diameter of the welding wire is 2.4 mm, assembling is conducted in a free state during welding, manual tungsten electrode argon arc welding is adopted, an internal wire adding welding method is adopted during bottoming, after the pipeline is filled with argon and is stable, root layer welding is conducted, and the temperature between layers is controlled to be smaller than or equal to 350 DEG C; and the method comprises the steps that firstly, grooves in the base metal sides of the dissimilar steel A and the dissimilar steel B are machined, the surfaces of the grooves and the outer walls, within 10 mm, of the two sides of the base metal are cleaned, and then horizontal fixed welding and vertical fixed welding are conducted. The welding method is used for the dissimilar steel of pearlite steel and austenitic stainless steel.