The models of pressure drop and filtering efficiency were introduced, the effects of path effective length, wall thickness, path number and path width on pressure drop and filtering efficiency were analyzed, and the mathematical model used to design and analyze was determined through comparing with test results. The importance of filter structural parameter to calculate the pressure drop and filtering efficiency was further analyzed and then the unmovable filter for test bench was designed based on the parameter of path number. The results showed that the path number and effective length were more beneficial to the optimization of diesel particulate filter and the path number had almost the same influence on pressure drop and filtering efficiency. The improved diesel particulate filter with the path number was applied and the pressure drop and filtering efficiency was 3.5 kPa and 90% respectively.