Abstract: In this paper,the effect of the steady-suction-based flow control method used to improve the aerodynamic performance of a lift type（H-type）vertical-axis wind turbine（VAWT）was numerically investigated. Suction slots were designed on both sides of the VAWT blade surface to control flow separations by removing low-momentum fluid. Both two-and three-dimensional numerical simulations have been performed on VAWTs with NACA0021 and NACA0018 blades,respectively in order to provide a baseline for flow control comparisons. Firstly,a two-dimensional CFD model was developed to explore the influence of the location of multiple suction slots on the blade surface on the power performance of the vertical-axis wind turbine. In addition,the effectiveness of two commonly used active flow control methods-suction and blowing that were used to enhance the wind energy utilization efficiency of the VAWT was then comparatively studied. Secondly,three-dimensional transient unsteady CFD simulations were also carried out to simulate the VAWT with suction on all blades for the purposes of comparing its performance with that of the VAWT having blades with the leading-edge serrations. From the obtained results,we found that the best suction control effectiveness can be attained with the multisuction slots placed within the 10%-15% chord length region from the leading-edge of the blade. Compared with the blowing,the net wind energy utilization efficiency of the VAWT with suction control can be increased more apparently for the whole range of tip-speed ratio. Moreover,the performance of the suction control is also superior to the leading-edge serration-based passive flow control in terms of maximizing the net wind energy utilization efficiency of the VAWT especially at low tip-speed ratio with the maximum increment of140%. Therefore,the suction flow control method shows great potential for practical applications due to its high efficiency and relatively low energy consumption.