Abstract: Coal samples of six outburst coal seams in coal-rich areas in Guizhou province were taken as research objects to analyze size grade of pore, fractal dimension, fractal characteristics and relationship between the fractal characteristics and gas adsorption or coal permeability by use of liquid nitrogen adsorption experiment and mercury intrusion experiment. The experimental results show that pores of the coal samples with different grades have good fractal characteristics, which can show porosity and pore distribution characteristics. The fractal dimension can be used to quantitatively analyze pore characteristics of coal samples. There is a positive correlation between the fractal dimension of micro pore of the coal samples and gas adsorption value. Gas adsorption capacity of coal samples in different coals is quite different. The fractal dimension of small pore reflects simple pore structures of coal samples and pore similarity among coal samples. The fractal dimensions of medium pore, large pore, pore fracture and micro fracture show that pore distribution trend of each coal sample is similar. Pores with some size grades develop badly, so measure for increasing the permeability of coal seam are needed to improve gas drainage effect.