Investigations on rock dynamics have been comprehensively focused on when the dynamic impact is perpendicular to the trend of the flaws, while understanding the dynamic mechanical properties and failure characteristics of rock with pre-flaws parallel to the loading direction remains unrevealed. In this study, impact tests are performed to experimentally study the dynamic mechanical properties, failure characteristics, and energy evolution of pre-flawed sandstone using the split Hopkinson pressure bar (SHPB) apparatus, in which the pre-flaws are parallel to the loading direction. The results show that for specimens, the dynamic loading rate and the number of flaws greatly influence the dynamic strength, peak strain, energy absorption rate, and failure behaviors. The dynamic strength increases exponentially with an increase in loading rate and decreases with an increase in flaw numbers. The fractal dimension of triple-flawed specimens is the largest at the same loading rate range. The failure modes of different pre-flawed specimens show a transition from tensile failure to tensile-shear failure with the increase of dynamic loading rate.