Abstract: Owing to the influence of Cu, thick-walled 15NiCuMoNb steel ring forgings used in pressure-bearing equipment are easily cracked or even scrapped during forging. Because of large wall thickness of the forging, the quenching effect is difficult to guarantee during heat treatment, and the risk of unqualified performance is also great. Through material composition design, steel-making composition control and forging process scheme design, the brittle cracking problem in forging forming was well solved. The optimum technological parameters of quenching and tempering were determined by heat treatment process test. Through the actual industrial production, the rationality of material chemical composition design and process parameters of forging, heat treatment were verified.