Abstract: The effects of chemical composition and heat-treatment on the impact toughness of a new type of micro-calcium steel with high-hardness (HRC> 58) and high-toughness (a_k> 40J/cm²) have been investigated. The results show that the micro-calcium play an important role in the improving of impact toughness of quened-tempered steels. The impact toughness of steels were also controlled by the content of chromium and the ratio of copper/silicon in steels.