Abstract: Abstract: Diesel engine is widely used in the fields of industrial and agricultural production and transportation for their good economy and dynamic performance. Unfortunately, diesel engines emit high quantities of particulate matter (PM) which is a potential risk to public health. Micron wood fiber is a kind of porous biological material that can be applied to filter PM emitted by diesel engine. In this paper, in order to increase the filtration efficiency and decrease filtration resistance, a wood fiber filter is developed, of which the internal structure is hollow and the external structure is like gear, and its advantages are low price, less requirement for diesel quality and large adsorption capacity for PM. In these respects, the gear-shaped wood fiber filter is promising in developing countries where the sulphur content is high in diesel oil. This gear-shaped wood fiber filter can be installed in a detachable DPF (diesel particle filter) whose temperature inside can be controlled below 220℃. First of all, based on the filter theory of fiber material, the filtration efficiency model of the gear-shaped wood fiber filter is established. Referring to the existing research and formula, the filtration efficiency of the gear-shaped wood fiber filter can be expressed by theoretical formula to be the function of wood fiber diameter, filling rate of wood fiber filter, thickness of filter and diameter of PM. Due to the diameter of PM ranging from 0.01 to 10 μm and mainly concentrating at around 0.1 μm, the recommended value of PM diameter is 0.1 μm. Then, through theoretical analysis and numerical calculation, the relationship curve between the filter efficiency and the influence factors is obtained. Lastly, a test bench of the filter performance is set up and used to verify the theoretical analysis results. In the test, we develope 10 gear-shaped wood fiber filters with different parameters according to the simulation results and set the speed and the load of the engine as 2 000 r/min and 50%. The results show that the experimental results are in good agreement with the theoretical results, i.e., the increasing of the filter thickness, the decreasing of the wood fiber diameter and the lowering of the filter filling rate will definitely improve the filtration efficiency of the gear-shaped wood fiber filter. For Lister Petter AA1 diesel engine, when the size of the DPF filter chamber is 140 mm in diameter and 150 mm in height, the filtration efficiency and the resistance of the filter with the wood fiber diameter of 15 μm, the filling rate of 0.3, the filter thickness of 12 mm are both in the most ideal range. At this point, the gear-shaped wood fiber filter has high efficiency and low exhaust resistance. When this filter works for 60 h from a new one, the filtration efficiency varies within a small range and the filtration state is relatively stable. When this filter works from 60 to 100 h, the filtration efficiency increases rapidly and reaches 96% at the end. However the filtration resistance exceeds the specified limit and a new wood fiber filter should replace the old one after it works for 100 h. Furthermore, the test results also show that the filtration efficiency of all filters made in test are more than 85%, which can meet the demand of the national standard of the diesel exhaust emission.