Abstract: To explore the influence of ammonium persulfate and chlorine dioxide on pore characteristics of lean coal and to optimize the oxidant which is more suitable for the coal reservoir reconstruction, lean coal samples from Daping Mine and Gaocheng Mine were collected for mercury injection experiment. The effects of ammonium persulfate and chlorine dioxide on porosity, fractal dimension, drainage pressure, pore volume, specific surface area and distribution of coal samples are discussed. The results show that chlorine dioxide can effectively improve the porosity of coal reservoir, reduce its specific surface area and fractal dimension, and ammonium persulfate may lead to a decrease in the overall porosity of coal reservoir, reduce the specific surface area of reservoir, and increase its fractal dimension. After the interaction of chlorine dioxide and ammonium persulfate, the proportion of large pore volume in coal sample increased, while the proportion of medium, small and micro pore volume decreased, making pores more uniform and the specific surface area of various pores did not change much. It is concluded that both chlorine dioxide and ammonium persulfate can oxidize and etch the reservoir of lean coal and reduce its methanophile ability. The effect of chlorine dioxide on desorption migration of CBM is better than that of ammonium persulfate.