Abstract: For 04Cr13Ni5Mo oversized martensitic stainless steel runner forgings, through the analysis of technical requirements and manufacturing risk points, the control measures for chemical composition, smelting, forging and heat treatment processes were proposed. By conducting high-temperature heating grain coarsening experiments on small specimens, the final heating temperature of the forging was determined. The small sample normalization and tempering process experiments was carried out to explore the matching relationship between material heat treatment tempering temperature and hardness. Using forging simulation software Forge, the upsetting deformation process of 200 t martensitic stainless steel ingots was simulated to analyze the temperature field, stress, strain and upsetting deformation resistance. The SIMHEAT heat treatment simulation software was used to analyze the temperature field, stress field and microstructure evolution of the heat treatment process of the runner forgings. The results show that a major breakthrough is achieved in the manufacturing of 500 MW impact type runner center body forgings.