The invention discloses a subzero treatment technology of AerMet100 steel. The subzero treatment technology comprises the following steps that solid solution treatment is carried out, concretely, theAerMet100 steel is subjected to the solid solution treatment, is subjected to heat preservation, is put into quenching oil for quenching, and is cooled to the room temperature; subzero treatment is carried out, concretely, the AerMet100 steel after being subjected to the solid solution treatment is subjected to the subzero treatment, the cooling rate is 3-5 DEG C / min, the subzero temperature is set as (-115) DEG C to (-125) DEG C, and after being subjected to the heat preservation, the AerMet100 steel is taken out and is subjected to air cooling until the temperature is recovered to the room temperature; and tempering treatment is carried out, concretely, the AerMet100 steel after being subjected to the subzero treatment is subjected to the tempering treatment, then is subjected to heat preservation, and is subjected to the air cooling to the room temperature. After the solid solution treatment, oil quenching is carried out in advance, the air cooling to the room temperature is carriedout, and then the subzero treatment is carried out, so that damage of rapid cooling and rapid heating on materials is avoided. In the subzero treatment process, a sample is cooled below -100 DEG C, so that the fatigue property of the AerMet100 steel is improved substantially.