The discrete element method (DEM) was used to establish the random stacking cylindrical activated carbon in the adsorption filter screen and the computational fluid dynamics (CFD) was used to simulate the flow field in the air purifier. On the basis of simulation and experimental verification, the hole shape, diameter and spacing of the filters with the least pressure drop and the most uniform flow field for air purifier were explored. The results showed that the pressure drop of the air purifier mainly occurred in the axial direction. The inlet gas could be averagely distributed by the pre-filter to improve the purification effect of the gas in the adsorption filter screen. There was a stable linear flow in the chemical filter, which was not conducive to adequate chemical reaction of harmful substances. And there was a phenomenon of reflux and retention in the gas chamber between the filters. The flow state of the activated carbon adsorption filter screen was extremely unstable, and the complex accumulation pattern of particles led to obvious high velocity and gully flow. The pressure drop of adsorption filter was three times higher than that of the other two filters, and it was also the main source of noise and energy consumption. The number of edges had no effect on the uniformity of the flow field and the pressure drop in the adsorption filter of the polygon filling hole structure. When the hole structure was changed to a circle, the pressure drop was reduced by 52 Pa and the energy was saved by 18.4% (49 W). When the diameter of the filling hole increased from 8 mm to 12 mm, the pressure drop was reduced by 48 Pa and the energy was saved by 19.4% (45 W). The filter spacing had no effect on the pressure drop of the air purifier, and the flow field in the adsorption filter with circular and small pore sizes was the most uniform.