Abstract: In the field of engineering structural materials, ultra-high strength steel (UHSS) has attracted significant attention due to its excellent mechanical properties. Based on traditional maraging steel, this paper increases the content of Co and Mo elements in the powder composition design. The alloy composition of the powder is designed as Fe-18Co-15Ni-8Mo-3Cr-0.5Cu-0.4Nb-0.4V-0.2Al. The ultra-high strength steel powder is prepared using a water-gas combined atomization method. After processes such as mixing with a binder, injection molding, debinding, sintering, and heat treatment in the metal injection molding (MIM) process, the ultra-high strength steel specimen is obtained. The powder and specimen are characterized and tested using various testing methods. The results show that the powder exhibits high sphericity, the sintered specimen has a density of 98.7%, and the mechanical properties are excellent (yield strength of 1824 MPa, tensile strength of 2053 MPa, and elongation of 7.9%). This study provides theoretical and experimental foundations for the preparation of ultra-high strength steel by MIM and is expected to promote its application in fields such as 3C products.