Abstract: Conventional mechanical property and fracture toughness of the 45CrNiMoVA steel conducted by different quenching and equal temper temperature were studied.The mechanism of the quenching temperature affected on its properties were analysed by surveying mechanical properties and fracture toughness and by viewing fracture surface under scanning electron microscope. It was shown that the quenching temperature has not any effect on 45CrNiMoVA steel yield and tensile strength and hardness in definite temperature,but the material fracture face contraction and elongation rate and impact work is very sensitivity to quenching temperature,1350 ℃ quenching may make tensile strength drop.