Selecting the red sandstone from a project of the Yunnan Diqing region to do the split Hopkinson pressure bar (SHPB) experiment and the scanning electronic microscopy (SEM) experiment under different moisture state and different pulse intensity, the paper studies the dynamic strength characteristics and the failure mechanism of waterbearing rock from macroscopic and microscopic point of view. The results show that: The strength of rock decreases with the increase of the moisture content in the static or dynamic uniaxial compression; According to the stressstrain whole process curves of the SHPB experiment, the waterbearing specimen has obvious volume compression deformation, higher peak strain and strain softening characteristics after peak, while dry specimen has higher peak intensity and its post peak stress drop rapidly. The compressive strength decreases with the increase of water content when pulse strength is the same, but increases with the increase of pulse intensity under the same water condition based on the dynamic compressive strength curve for each specimen. The SEM images show that the particle structure of watersaturated rock is loose and swelling, and the impact failure mechanism is dominated by the fracture of initial microcracks and mineral particle or phase boundary, performance as dynamic compressive strength reduction, while the particle structure of dry rock is compact and the impact failure mechanism also include the fracture of mineral particles cut directly, and this shows that the strength increases.