An experimental study of the effect of burst ratio for a DBD plasma actuator on control- ling the separated flow is investigated in this paper. Time-averaged pressure measurements and PIV image acquisitions were conducted around a NACA0015 airfoil at the post-stall (αstall + 1deg) and the deep-stall (αstall + 3deg) angles in the condition of the Rec = 63; 000. Experiments were conducted with two types of burst frequency, F+ = 1and6, based on our previous researches. Results of time-averaged pressure measurement show that actuation with the high burst ratio can enhance turbulent transition strongly. Phase-locked PIV visualization shows the generation of multiple vorticies from the shear layer with burst actuation and the process of the vortex-pairing. This visualization reveals that F+ = 1, BR = 50% actuation generates twice vorticies than the other F+ = 1 actuations at the post-stall angle.