In 0.48m diameter flat bottom stirred tank, double layers impeller of six vertical fin-type and ordinary type were used,respectively.In the both cases, we studied the mixing times of single phase fluid in stirred tank.The results showed that compared to the ordinary type impeller, the mixing time of fin-type impeller was reduced greatly with the same rotational speed and mixing effect.Therefore, at the same time reducing energy consumption of the fin-type impeller, enhancing the mixing effect of liquid fluid.