Abstract: In oleum, a series of the catalyst such as sulfate compound, transition metal compound, iodine compound that could be used for catalyzing low concentration of CBM were observed. The experimental results show that catalytic effect of iodine was the best, conversion rate of low concentration of CBM could reach 79.69% and the methane selectivity reached 83.74%.Then, the effect of concentration of iodine catalyst was studied. With the concentration of iodine catalyst increased, the conversion of low concentration of CBM increased untill it reached a maximum and then dropped down. According to the liquid partial oxidation reaction mechanism of methane in oleum solution, the liquid partial oxidation reaction mechanism of low concentration of CBM in oleum solution may be the electrophilic substitution.