The invention relates to a postweld heat treatment process method for a shaft forge piece. No heating component is arranged in a hearth, a heated air circulation channel is formed in the side wall of the hearth, and a variable frequency high-temperature centrifugal fan drives heat to heat a workpiece. Meanwhile, a full-scale simulated part in a ratio of 1: 1 is manufactured so as to further grope and determine a novel heat treatment process through repeated tests, wherein the insulating temperature is set at 732 DEG C+14 DEG C/-28 DEG C, the insulating time is 3h, and the temperature increasing and decreasing rate is 30 DEG C/h. According to the method provided by the invention, heat treatment defects caused by improper heat treatment processes and equipment of the shaft forge piece are effectively prevented, so that the whole product piece is good in performance and quality. The achievement is of very high application value in engineering and has far-reaching social meaning. The method provided by the invention gets rid of defects such as severe oxidation of heat treatment and excessively high local temperature of the shaft force piece caused by adopting common heat treatment equipment and process method, greatly reduces the risk that the weld joint cracks, prolongs the service life of the part and increases the safety coefficient.