Abstract: To replace 30CrNi4Mo steel with new bainitic steel,the microstructure,mechanical properties and repeated impact fatigue properties of the two steels after different heat treatments were studied.The results show that the 30CrNi4Mo steel had high tensile strength and impact toughness after austenitizing air-cooling or oil-cooling and low temperature tempering.With the increase of tempering temperature,the microstructure transformed to sorbite from tempered martensite and retained austenite after quenching,the strength and toughness matched well after oil-cooling and high temperature tempering,the impact fatigue life was always higher than that after air-cooling or oil-cooling and low temperature.The new bainitic steel had good matching of strength and toughness after quenching or normalizing and low temperature tempering.The impact fatigue life after normalizing and low temperature tempering was longer than that of after quenching and low temperature tempering.The impact fatigue life of the new bainitic steel was long at the state of air-cooling and low temperature tempering,indicating that it could replace with 30CrNi4Mo steel to be used as impact resistant loading material.