Abstract: Based on damage mechanical theory,through axial loading low cycle fatigue test controlled by different strain amplitudes adopting smooth rotundity-section specimens,damage characteristics of tensile-unloading modulus,compression-unloading modulus and cyclic elastic modulus of 10CrNi5MoV high strength steel were studied.The results manifested that damage of three types of elastic modulus depends on strain amplitudes and the higher the strain amplitude,the quicker damage of the three types of modulus.Before failure of the smooth specimen,damage of the three types of modulus had no obvious changes and just when the specimen failed,damage variable D of three types of elastic modulus tended to 1,which provides reference for engineering application of 10CrNi5MoV high strength steel.