This article concerns developing molybdenum nickel steel through increasing chromium content from 0.6 to 7.81 %. Three steel grades were produced in an induction furnace with a capacity of 30 kg. The chemical composition of the produced steel grades was determined. It was found that carbon content ranged from 0.044 to 0.056%, silicon content was less than 0.08%, manganese percentage was not more than 0.15%, molybdenum content ranged from 1.35 to 1.54 %, and nickel content ranged from 0.73 to 1.1%.  The normalizing process was carried out for the produced steels, followed by the free forging process. The start forging temperature was 1100 ^oC and the finishing forging temperature was 950 ^oC. The forged steels were solution-treated to dissolve precipitates. Mechanical properties at room and high temperatures (300, 500, and 700 ^oC) were measured. Increasing chromium content improved the mechanical properties at room and high temperatures (up to 500 ^oC). It was found that the yield and ultimate tensile strength increase from 370 & 520.1 MPa to 959.18 & 1163.8 MPa respectively at room temperature, and from 270.5 & 584.5 MPa to 844.81 & 1081 MPa at 500 ^oC.  The developed steel (with 7.81 % chromium content) was nominated to be used at high temperatures at different parts for nuclear reactors and in a boiler of steam power plants up to 500 ^oC.