The invention provides a method for brazing a martensitic stainless steel rectifier assembly through vacuum. The method is characterized in that foil shaped brazing filler metals are filled among blades so as to ensure brazing clearances of the rectifier assembly. According to the method, the positioning method of adding H1Cr11Ni2W2MoV welding wires is carried out, and the welding is carried out in a symmetrical and crossed manner; a welding point is Phi 3 in diameter, so that little welding stress is brought to a part; the deformation of the part is reduced in follow-up brazing, and an argon arc point is out of cracking; an annealing process is added after brazing under vacuum, so that the mechanical performance of the part is improved; meanwhile, a brazing fixture manufactured by graphite is used, and a layer of Al2O3 is coated on the surface of the brazing fixture, so that the brazing fixture can be prevented from being adhered with the part after the brazing, and the brazing fixture cannot be deformed during brazing at 1055 DEG C; and tests show that product percentage of pass is 100%, brazing seams are nicer in appearance and higher in quality after the brazing, and the brazing seams are continuous and smooth in appearance.