Abstract: In order to study the aerodynamic performance of the straight blade vertical axis wind turbine（VAWT）,the three-dimensional numerical simulation on the flow field of the wind turbine is simulated for its optimization design using the software Fluent based on the technology called sliding grids.Then an analysis has been taken,including the variation of the velocity field,the distribution of the velocity field on different sections at the same time,and one blade’s distribution of the velocity and pressure field on different places in a period.At the same time,the wind-power utilization coefficient has been obtained by using its torque coefficient and related formulas.The result shows that the change of the flow field will periodically be under fully developed flow area.The wake area constantly narrowed.The distribution of the velocity and pressure is related to the phase angle.And a better wind turbine designing model which has a deformation has been proposed from this work.