Coal is a non-uniform porous medium. The degree of porous development is closely related to absorption-desorption characteristics and flow characteristics of coal seam gas. In order to investigate pore structure of briquette, it is studied the characteristics of porous development of briquette with different coal particle sizes like 4.00~1.70 mm, 1.70~0.38 mm and 0.38~0.18 mm by using CF-2000P polarization analysis software and Fractalfox2.0 fractal analysis software. Testing result shows that with the decrease of coal particle size, briquette pore radius decreases, the total number of pores and fractal dimension increase. And the more the pore develops, the more uniform the pore distributes.