The invention relates to a braze welding method for hard alloy, and belongs to the field of braze welding of hard alloy. The braze welding method for the hard alloy comprises the steps that elemental cobalt is introduced between the hard alloy and brazing filler metal, and then welding is conducted. According to the braze welding method for the hard alloy, by introducing elemental cobalt between the hard alloy and the brazing filler metal, a liquid phase area with the high cobalt concentration is formed in the interface of the brazing filler metal and the hard alloy, and cobalt diffuses towards the hard alloy direction and the brazing filler metal direction from the interface separately, so that cobalt diffuses towards the hard alloy direction from the interface, the above-mentioned diffusion trend is balanced with the diffusion trend of cobalt in the hard alloy to the interface, therefore, the cobalt diffusion migration phenomenon is effectively inhibited, and the welding quality of hard alloy braze welding products is improved.