The use of advanced high-strength steels is an effective way to reduce the weight of vehicles while guaranteeing passive safety. In order to promote the application and promotion of 45Si2MnCr2Mo ultra-high strength steel (UHSS) on armor protection, it is critical to understand their dynamic deformation behavior of these steels. In this paper, dynamic mechanical experiments were carried out on 45Si2MnCr2Mo UHSS with different Ni/Al contents by using the split Hopkinson pressure bar (SHPB). The effects of different Ni/Al contents on the dynamic compressive strength, dynamic mechanical behavior and fracture absorption work of UHSS were studied. The results show that the comprehensive performance of ultra-high strength steel is the best when the Ni content is 3%. At high strain rate (1500 ~ 3500 s−1), the dynamic compressive strength is maintained at around 2500 MPa, the maximum strain is 15%, and the fracture absorption energy is 414 J/mm3. When 0.3% Al is added, the dynamic compressive strength of ultra-high strength steel is reduced by around 80 MPa, the maximum strain is 14%, and the fracture absorption energy is 387 J/mm3. Adding Ni element can improve the dynamic mechanical properties of ultra-high strength steel, but when Al and Ni are added at the same time, it is not conducive to improving the dynamic mechanical properties.