Abstract: In the paper,series temperature impact tests of D36,14MnVTiRe and 10CrNiCu steels are carried out on instrumented impact tester.The results show that ductile-brittle transition temperature of these steels is lower and it is more accurate to use crack propagation energy W_p as criterion for the ductile-brittle transition temperature.Fracture energy is consumed mostly on crack extension when test temperature is higher than ductile-brittle transition temperature;while it is consumed mostly on crack formation when test temperature is lower than ductile-brittle transition temperature.