Abstract: Low-alloy high-strength steel CF62C was cold-treated at the temperature ranged from room temperature to -50 ℃. Charp-V impact tests were carried out for those cold-treated samples and room temperature samples. Absorbent impact energy, microstructure and fracture surface were analyzed. The results showed that steel CF62C had favorable low-temperature impact toughness after cold-treatment at the temperature from 0 ℃ to -40 ℃, as well as at room temperature. At -40 ℃, the absorbent impact energy of steel CF62C was 300 J, and then decreased to 135 J at -50 ℃, where brittle fracture was observed on the fracture surface. The brittle transition temperature of steel CF62C was -50 ℃.