Abstract: The dynamic compressive experiments on sands pecimens under passive confining pressures are carried out using a 50 mm split Hopkinson pressure bar. The dynamic response behaviors of sands with different relative densities and water content at medium high strain rates are investigated. The effects of the relative density and water content on the dynamic compressive behaviors of sand are also studied. It is indicated by the test results that: (1) The dynamic response of sands under the dynamic compressive action shows obvious strain rate effect. The peak stress of dry sand increases with the increase of strain rate, and the peak stress of wet sand first increases and then decreases with the increase of strain rate. The peak strain of dry and wet sands first increase and then decrease with the increase of strain rate. (2) The density of sand has an important effect on its dynamic compressive behaviors. The peak stress and peak strain of sand increase with the increase of relative density. (3) The water content of sand can impact its dynamic compressive properties in a certain extent. The peak stress and strain first increase and then decrease with the increase of water content. There is a dividing water content and the varying trend of the peak stress and strain are different when the water content is larger or less than the dividing water content. For the tests performed in the current study, the dividing water content is 6% for the sand specimens with the relative density of 0.9.