Active skin-friction drag reduction is experimentally investigated using periodic blowing through one array of longitudinal slots. The drag reduction exhibits a strong dependence on the blowing amplitude and frequency. The maximum drag reduction reaches 70% at 33 wall units downstream of the slots, while the drag is not fully recovered to the natural state until 460 wall units. There is a pronounced change in the corresponding near-wall turbulent flow structure. The near-wall large-scale streaky structures are replaced by more stable and smaller-scale streaks. Meanwhile, the measured predominant component of the mean turbulent kinetic energy dissipation rate is found to jump by more than four times, along with a reduction of the Taylor’s microscale by one half. The mechanisms behind the substantial drag reduction are proposed. Empirical scaling analysis is also conducted.