With the dramatically growing use of agricultural highpower tractors, comfort of cab is an important problem in China. Because of the indirect impact with low comfort of cab, the productivity is restricted. Health of tractor drivers was also undermined by low comfort of the cab. 〖JP3〗Highpower tractors play an important role in tilling machine. The PM concentration in ambient air is very high (512mg/m3). 〖JP〗Foreign mainstream tractor comfortable cabs are enclosure cabs to protect PM into cabs. In the field research, enclosure cab can protest PM10 and PM25 very well except tilling work. The PM10 and PM25 concentration cannot reach the human healthy standard when tractor is tilling. The foreign research of PM cleaning system in tractor cab is at an initial stage and the research in Chins is empty. So, the PM research is meaningful. The concentration of PM10 and PM25 simulation was done based on collection data in other researches. Firstly, the concentration variety model and cleaning model were deduced according to the mass conservation theory. Then, the simulation was done under different cleaning methods (return, supply and freestanding filter) and cleaning efficiency (50%, 75% and 90%) by IAQx11-PM. The results showed that the relative cleaning efficiency of return and supply were 92.78% and 96.13%, respectively. These two methods could reach the international human healthy standard. The PM10 and PM25 concentrations in supply method could be lower than 800μg/m3. Although the relative cleaning efficiency of freestanding filter was between 48% and 66%, the international human healthy standard still could not be reached. The curve of PM10 and PM25 concentrations showed that supply method was the fastest to get stable statues (1h). Finally, the human inhalation exposure was calculated. It was indicated that HVAC design method should be used in comfort cab. This method could save the volume of air conditioner volume and control the temperature and PM concentration.