The flow resistance of planar air filter is measured. The results reveal that the flow resistance accelerando increases with the increase of air velocity and the filter core resistance accounts for about half of the total air filter resistance. When the air inlet flux is 120 m 3/h, the total resistance is 915.3 Pa and the filter core resistance is 426.4 Pa. A 3D numerical simulation using the porous media jump model is established, based on the filter core flow resistance parameter obtained by experiment. The results show that the simulation results are in good agree with the experimental results and the maximum deviation is 5.67%. The filter core flow resistance also accounts for about half of the resistance, and the outlet resistance is the main part of the other half resistance, the rest 15% is the wall resistance. And, an improved model is put forward and the simulation results show that the resistance of the improved model apparently decreases. When the air inlet flux is 120 m 3/h and the total resistance is 588.2 Pa, the resistance of the improved model decreases by 32.2%. The method of increasing the air filter flow cross sectional area is an effective way to reduce the resistance and increase air inlet flux.