Abstract: To investigate the influence of strain rate on stress-strain relation and dynamic strength, uniaxial compression strength, elastic modulus and poisson's ratio of mortar were measured by quasi-static experiments.The one-dimensional stress experiment was carried out by using split Hopkinson pressure bar(SHPB), dynamic damage and stress-strain relation of the cement mortar with various length-diameter ratios at different loading rates were obtained,and the relation of DIF(dynamic strength increase factor) and strain rate was studied.The results show that dynamic compressive strength increases significantly with increasing strain rate.The DIF with thin specimens are smaller than those with thick specimens when diameters are the same, but length-diameter ratios are different.By comparing the recovered specimens, as the strain rate increases, the damage of the specimen increases, and the fragment size decreases.It is found that the failure energy increases with the growing of the strain rate.