Concrete structures prior to being subjected to dynamic loadings such as earthquake have already withstood initial stress. So the study of strain-rate sensitivity of concrete should be closely related to the initial loading history that concrete experiences. Yet majority of available documents concerning the dynamic properties of concrete do not take the initial static loading history into consideration. In this study, experiments were carried out to investigate the effect of initial static stress on the dynamic strength and deformation characteristics of concrete. A prescribed load was initially applied on the specimen at a very low strain-rate and then a dynamic load was applied at a high strain-rate up to failure of the specimen. The relationship between dynamic strength factor and the initial stress is obtained. The comparison between the results by the proposed formula and those by experiments in this study indicates a good agreement. The stress–deformation curves obtained in the tests show that the initial static loading history plays an important role in the total deformation behavior of concrete. An explanation to the physical mechanisms of high strain-rate strength enhancement with different initial static stress was proposed.