Abstract: The characteristics of dynamic fracture of the steel used in the constructional elements of heavy-duty excavators which worked in cold mining environment were investigated by simulating the real operation state.The reasons of brittle fracture were analyzed. It was shown that the ductile-brittle transition temperature in the 15MnV steel was sensitive to loading rate. As digger of the excavator dashed on the recks, the ductile-brittle transition temperature of the steel could be increased to -12℃.This temperature is close to the failure environmental temperature of the steel. It was found that the metallugical quality and treatment state of the steel had an obvious influnce on its fracture toughness and ductilbrittle transition temperature.