Abstract: In order to further enhance the mechanical properties of 18Ni maraging steel, adding trace elements such as niobium, vanadium or boron into the steel, then it was investigated the influences of different trace elements on microstructure and mechanical properties. The results show that the steel adding 0.1wt% niobium had finer grains than that adding 0.1wt% vanadium or 0.01wt% boron, whose grain size in solid solution state reached to 10.2 grade. After aging, the intermetallic compounds distributed more uniformly and dispersively, so that the tensile strength of steel was as much as that of M300 steel, while its elongation and reduction of area decreased by 2.1%.