Pollutant emissions of diesel engine are mainly particulate matters, nitrogen oxide(NO_x), hydrocarbon (HC), carbon moNO_xide(CO), etc.The NO_x, sulfide and particulate matters can form aerosol in the atmosphere, which is one of main causes leading to fog and haze.The concentration of small and medium scale particles such as PM2.5 and NO_x is increasing with the wide application of diesel engine.The fog and haze weather occurs frequently, which has negative impacts on human health.It is quite necessary to carry out research on reducing particulate matters emitted from diesel engine.The diesel particulate matters and NO_x emissions can be effectively controlled by adding the oxygen-containing fuel in the reaction process combined with the technology of the exhaust gas recirculation(EGR), which yet has multiple effects on the microstructure and oxidation behavior of the diesel engine particulate matters.In order to analyze and comprehend the effect of particle structure and fractal characteristics, a particulate matter sampling device was employed to collect the diesel engine particulate matters, which took oxygenated fuels combined with the technology of EGR into consideration.And the effects of different EGR rate (0%, 10% and 20%) on the particulate matters, which were produced in the combustion of N-butanol/diesel blended fuel with 10% N-butanol(N10), were studied with the thermal field emission scanning electron microscope (SEM) and high resolution electron microscopy(TEM), and the results were analyzed by the image technology.To be specific, the changing rule of physical structure parameter including the particulate matter microstructure, the average particle size of particulate matter group and the fractal dimension were analyzed, as well as the fringe separation distance and the fringe length distribution of basic carbon particles.It could be well observed that there was obvious clusters structure of particulate matters formed by combustion under 3 different conditions: N10EGR0, N10EGR10% and N10EGR20%.What was more, the range of particulate matter size was mainly concentrated between 30 and 70 nm which showed the normal single peak distribution.And the size of particulate matters demonstrated the pattern moving to larger figures gradually with the EGR rate increasing.Also the average size of particulate matter of N10EGR20% increased by 19% compared to N10EGR0.The gradual decreasing of box dimension indicated the fact that the intergranular degree of clusters gradually weakened.On the other hand, the basic carbon particles under different EGR conditions presented the similar structures, which looked like spherical carbon layer fingerprints.The basic carbon particulate matters were composed of 2 parts, the basic kernel layer and the shell.The basic kernel layer was the amorphous carbon structure, and the shell was the structure of graphite crystallite.Moreover, with the increasing of the EGR rate, the basic kernel layer was arranged more disorderly and the shell carbon particulate matters presented more irregular graphite crystal structure.To summarize, the average fringe separation distance of basic carbon particles was increased gradually as well as the average tortuosity distribution, and the average fringe length distribution was decreased with the increasing of EGR rate.The oxidation activity of particulate matters was improved with the adoption of EGR.This study can provide a theoretical reference for the formation mechanism of particulate matters and the measures to reduce the particulate matter emission of diesel engine by oxygenated fuel and the technology of EGR together.