Abstract: The excess generation of coalbed methane(CBM) during coal and gas outbursts has been an important con- tent of coal geology. The pyrolysis and the sub-high-temperature and sub-high-pressure deformation experiments of coals were systematically investigated. Based on mechanochemistry research,a new opinion is proposed. It is founded that the deformation of coals under tectonic stress can change the chemical structure and promote the breakage of side chains and functional groups,thereby resulting in gas generation. Compared with previous research,the same rank of coals in the pyrolysis experiments and the sub-high-temperature and sub-high-pressure deformation experiments will generate different gases. Mechanochemistry studies indicate that the action of mechanical force can not only cause the degradation and chain scission of polymers,but also bias reaction pathways. According to that study,the reason why the same rank of coals in the pyrolysis experiments and the sub-high-temperature and sub-high-pressure deformation ex- periments could generate different gases may be due to the different degree sensitivity of different chemical bonds,and thus mechanical force changes the chemical reaction pathways.