Fan is a major part of the cooling system in the vehicle, axial flow fan is used very common recently. In order to improve the cooling capability, cooling fan’s structure has been changed; experiment research and numerical simulation are done for it. The result show that after adding guide vane to axial flow fan, its mass flow increases. At the same speed, the mass flow is increased by 20% when a rear guide vane is installed, and 15% of mass flow increase when the front guide vane is installed, which indicates that a mixed flow fan could be increased in flow and improved in performance if the guide vanes are installed. Rear guide vane is better than front guide vane in the aspect of improving mass flow. Take front guide vane as an example, adopting the NUMECA for numerical simulation, the result is as similar as the experiment’s.