Abstract: The phenomenon emerging some bright spots in observation window during gas explosion was analyzed. Results show that it is the soot particles with high thermal radiation property that yield this intense light. The characteristics of soot aperture and surface structure were investigated based on low-pressure nitrogen gas adsorption (LP-N₂GA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) methods. The results show that soot particles possess a specific surface area of 1.507m²·g^-1(DFT) and pore volume of 4×10^-3cm³·g^-1. The images of SEM illustrate that the soot particle is composed of abundant spherical aggregations with a diameter range from 4μm to 50μm. The pores at the particle surface are well developed, some of the particles exhibits an ablation feature. The soot aggregates are botryoidal and some of primary particles bond together, the diameter of majority particles are of 100nm from TEM images. The graphite layer with lattice fringes can be seen from the primary particles. The infrared spectroscopy analysis shows that soot particles contain a large amount of polycyclic aromatic hydrocarbon, aromatic series and other functional groups.