Abstract: Dielectric barrier discharge (DBD) actuator has the advantages of light weight, no moving parts, ease of use, and quick response, and have received extensive attention in flow control applications. Plasma turbulent boundary layer drag reduction is one of the many applications of DBD flow control, and the DBD turbulence drag reduction mechanism needs to be further explored. The effect of plasma actuator on the skin-frictional drag of turbulent boundary layer on a flat plate was investigated experimentally at an incoming velocity of 10 m/s. The oil film interferometry was used to measure the change of skin-friction, and the hot wire anemometer and particle image velocimetry (PIV) were used to obtain the velocity distribution in the boundary layer. The results indicate that under the action of the plasma actuator, the measured skin-friction coefficient decreases. Plasma excitation suppresses the development of coherent structures by reducing the velocity of the boundary layer buffer and the logarithmic region, reducing the Reynolds stress as well as the magnitude of the turbulent kinetic energy, which results in drag reduction.