Dynamic compression tests with a high strain rate (1000--4200 s -1) were carried out on the as-deposited and heat-treated samples of AerMet100 ultrahigh strength steel fabricated by laser additive manufacturing using a split Hopkinson pressure bar (SHPB), and the microstructures and impact fractures of the samples were observed. The results show that the strain rate sensitivity of the AerMet100 steel samples fabricated by laser additive manufacturing is high, and the strain rate hardening effect of the material is obvious. Heat treatment can improve the dynamic impact performance of the laser additive manufactured AerMet100 steel. After solid solution treatment at 885 ℃ for 1 h, oil quenching, cryogenic treatment at -73 ℃ for 1 h, and tempering at 482 ℃ for 5 h, the AerMet100 ultrahigh strength steel samples fabricated by laser additive manufacturing show the optimal combination of strength and toughness and an excellent dynamic impact performance. When the tempering temperature increases to 494 ℃, the dynamic compression strength of the samples decreases.