Air filter as the heart of the car filtering the dirty air entering the engine which plays a key role in protecting the engine. In this work, because the performance of the air filter has a direct impact on the engine's power performance and economy, a standard k?? turbulence model was used to simulate the internal flow field and resistance characteristics of macrohoneycomb air filters with different structures based on the theory of porous media, thus to optimized the structure and improved its performance. The model adopted the same filter element(pleat height h=5 mm), while the series of combinations of the inlet and outlet shapes of the housing were round and round (scheme 1), round and ellipse (scheme 2), ellipse and round (scheme 3), ellipse and ellipse (scheme 4), respectively. Then the optimized housing was combined with honeycomb filter element with pleat heights of 5, 10 and 15 mm. The results showed that the flow field distribution of scheme 2 was more uniform than that of schemes 1, 3 and 4, and the pressure drop increased approximately linearly with the increase of flow rate. When the flow rate was less than 60% of the rated flow, the values of pressure drop of these four schemes were approximately equal. However, the pressure drop of scheme 2 was smaller than that of schemes1, 3 and 4 when the flow rate was greater than 60% of the rated flow. Therefore, the housing of scheme 2 was more reasonable. For this structure, the difference in the pleat height of the filter element had a certain influence on the flow filed distribution of the air filter. Furthermore, the pressure drop decreased firstly and then increased in the range of pleat height studied. Therefore, there was an optimal pleat height to minimize the pressure drop of the honeycomb air filter, which provided theoretical guidance for the optimal design of air filter.