Abstract: Large-scale vortex shedding is prone to occur on the suction surface during dynamic stall process of the airfoil,resulting in a sharp decline in aerodynamic performance due to stall. Numerical simulation of the S809 airfoil is carried out by using sliding mesh technology and SST k-ω turbulence model,and the effect of the leading-edge steady suction is studied on dynamic stall flow control and aerodynamic characteristics. The results show that the suction effectively suppresses the dynamic stall vortex shedding,increases the pressure discrepancy on both sides of the suction/pressure surface and improves the aerodynamic performance. The maximum average lift coefficient can be obtained by steady suction at 0.05c from the leading-edge of the airfoil,while there is sustained decrease of the corrected drag coefficient as the suction position closing to the leading-edge. When the suction momentum coefficient is 0.025 and the suction distance from the leading-edge is 0.15c,the corrected lift-drag ratio is largest in the studied angle of attack compared with the original airfoil. Moreover,suction energy consumption is positively correlated with the suction momentum coefficient,increasing with the decrease of the suction gap distance from the leading-edge.