As a micro-damage test method, scratch tests are employed to extract the plastic and fracture parameters of materials. In this paper, scratch tests of 18CrNiMo7–6 alloy steel were conducted to investigate the effects of scratch velocity and temperature on its scratch responses. Using a scratch model based on linear elastic fracture mechanics, the fracture toughness of 18CrNiMo7–6 alloy steel has been characterized. The effect of temperature and loading rate on the fracture toughness of 18CrNiMo7–6 alloy steel was also explored. The results indicate that the scratch depth, scratch width and tangential force of 18CrNiMo7–6 alloy steel increase with an increase in scratch velocity while increase with temperature. The scratch hardness increases with the scratch velocity while it decreases withtemperature. Fracture toughness increases with increasing loading rate and decreasing temperature. The work of this paper has a certain reference value for the study of fracture toughness of metal materials considering environmental influences.