In this paper,a low-alloy structural steel Cr-Mo system has been studied. Completely quenching process was performed on a novel steel for perforated gun tube and the influences of the quenching temperature, holding time and tempering temperature on the microstructure and properties of the experimental steel had been investigated. The results show that, the grain of the experimental steels became larger with the increase of the quenching temperature. The hardness of the quenched steel increased firstly and then decreased with the increase of quenching temperature.At the same quenching temperature, hardness and grain size changed little, with the holding time extending.With the increase of the tempering temperature,the hardness and strength of the steel quenched at the same temperature decreased,but shrinkage of section and the impact energy increased. When the quenching temperature was 900℃,holding 40min and tempering temperature was 560℃,holding 80min,the steel achieved a yield strength of 927MPa that was higher than 130ksi.Its hardness was HRC31.2,while its vertical and horizontal impact energies reached 74.5J and 119.7J.Thus,the overall performance is the best.