The invention discloses a diffusion welding method for a fixing supporting plate with a supporting plate head. The method specifically comprises the steps that linear cutting is carried out on a blank, grinding machining and other treatment are carried out on the surface of a to-be-welded surface, assembling positioning is carried out before welding, a compression amount supporting block is presetto ensure the compression amount, the corresponding welding parameters are controlled to carry out diffusion welding, the compression amount is checked after welding, welding seam metallographic inspection is carried out and other steps to complete the diffusion welding for the fixing supporting plate with the supporting plate head, wherein the welding percent of pass is larger than 95%. According to the method, the diffusion welding method is adopted to complete welding of the fixing supporting plate with the supporting plate head, the diffusion welding link for portions between layered plates of a conventional three-layer plate superplastic forming diffusion welding supporting plate is removed, hollowing of a strengthening rib triangular region of the inner cavity of the supporting plate is avoided, the faults of bulging and cracking of multi-layer plate diffusion connection fixing supporting plate are overcome, meanwhile, the supporting plate and the supporting plate head are of anintegral structure; and the diffusion welding process for the fixing supporting plate with the supporting plate head has the multiple advantages that the technological process is simple, the qualityis easy to control, the quality is stable, the consistency of inner molded surface and the outer molded surface of the fixing supporting plate is good, the size precision is high, and the like.