Abstract: Towards properties deterioration of casting 10CrNi3MoV steel after thermal processing and normal tempered,cycle quenching heat treatment was performed and the mechanical properties, microstructure as well as grain size were investigated. The results showed that with cycle quenching of 3 times at 860℃ plus tempering at 630℃ for 3 hours, the grains of steel were effectively refined,the low temperature toughness was significantly improved,so a better matching of strength and toughness was obtained.