The invention relates to a hydrogen-expanding annealing method for a post-forging step of a forging material. The method is characterized by comprising the following steps: 1) preserving the heat for a forging at 230-260 DEG C for 20-45 minutes; 2) after preserving the heat, quickly heating to 400-480 DEG C within 30 minutes for secondary heat preservation for 10-20 minutes; 3) after secondary heat preservation, heating to 550-620 DEG C within 8-10 minutes for preserving the heat and dehydrating; 4) quickly cooling to 400 DEG C within 10-15 minutes for 5-8 minutes; 5) cooling to 260-300 DEG C within 3-5 minutes; 6) preserving the heat for the forging obtained in the step 5) for 30-40 minutes; 7) after preserving the heat in the step 6), continuously cooling to 210-220 DEG C within 5 minutes and discharging.