Abstract: Computational fluid dynamics（CFD）is an effective method to study the aerodynamic performance of vertical axis wind turbines（VAWTs）. At present,the two-dimensional（2 D）Unsteady Reynolds Average Navier Stokes（URANS）method has been widely used to analyze the aerodynamic performance of VAWTs,but its accuracy is limited. In this paper,the accuracy and feasibility of the 2 D URANS,2.5 D URANS,2.5 D LES and 3 D URANS CFD modeling techniques are studied for wind turbine aerodynamic performance analyses by comparing with the experimental results. Compared with the SST k-ω method,the LES method can provide more accurate results under the dynamic stall conditions. The significant improvement of the 2.5 D LES simulation results show that the neglect of blade tip vortices may not be the main reason for the excessive prediction power of both 2 D and 2.5 D URANS,but may be due to the internal defects of the equation. Considering the calculation accuracy and cost of both 2.5 D LES and 3 D URANS models,2.5 D LES can be regarded as an effective method to study the aerodynamic performance of VAWTs,especially for the start-up condition of VAWTs.