Flow field induced by the plasma actuator in quiescent air was measured by particle image velocimetry system. Boundary layer flow control in flat plate by the plasma actuator was investigated experimentally. Experimental results showed that the relation between exciting voltage and induced velocity magnitude was linear, but the influence of supply frequency was not evident. Mechanisms of plasma flow control were preliminarily ascertained to be results of collisions and temperature increase. Numerical simulation results showed that the thermal effect of the plasma was evident without incoming velocity. Methods of increasing plasma actuator's intensity were introduced briefly.