The aim of this study is to evaluate the effects of exhaust gas recirculation (EGR) on particle size distribution, microscopic morphology, compositional elements, and oxidation characteristics of particles from coal liquefied fuel engine. Particles from the engine fueled with coal liquefied fuel were collected under different EGR ratio (0% EGR, 15% EGR) and exhaust gas composition (15% N₂, 15% CO₂ and 30% CO₂). The micro structure and oxidation characteristics of the particles were analyzed by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermogravimetric analyzer. The results showed that when the EGR rate is less than 15%, the particle size shows a single peak normal distribution. The peak diameters of particle size distribution were 60.4, 60.4, 69.8 and 52.3 nm in the condition of different EGR ratio of 0% and 15%,different composition of 15% N₂ and 15% CO₂ respectively. When 30% CO₂ was introduced, the particle size showed a bimodal normal distribution with particle sizes of 14.3 nm and 52.3 nm respectively. After the introduction of EGR and N2, the particle group becomes compact and was not easily oxidized. After the introduction of CO₂, the particle group became loose and easily oxidized. Without EGR, the particle structure was mainly chain-like, and introducing 15% EGR and 15% N₂, the particle structure was mainly clustered.