This thesis studies the influence of the oscillations of piezoelectric plate upon velocity distributions in a duct flow. The methodology in this thesis is to analyze the variation of velocity and spectrum of the flow field using the distribution angle of the velocity field. The transportation mechanism and the parameters of active control can then be understood with the knowledge of the flow field. In the experiment, we use a regular piezoelectric material as an actuator. The four piezoelectric plates are arranged in spanwise and set up in front of the duct vertically. In addition, an amplifier and a function generator are used to output the sinusoidal wave with a specific frequency in order to disturb the flow field in the duct using oscillation. Low-speed wind tunnel is used to provide uniform flow. Velocity distribution is measured using different experimental parameters, which are resulted from the various compositions of wind velocities and piezoelectric-plate oscillating frequencies. Qualitative analysis is obtained by flow visualization, and quantitative analysis is measured with Hot-Wire Anemometry. The experimental results show that piezoelectric plates oscillating in lower frequency disturb flow obviously. Although piezoelectric plates oscillating in higher frequency has faster transporting than those in lower frequency does, they do not help as much in flow field mixture as the lower frequency ones do.