Abstract: There are significant differences on the gas composition and isotopic composition between biogenic coalbed gases and thermogeniocoalbed gases,which has an important significance to coalbed methane resource exploration. In order to beter serve the exploration of biogeniocoalbed gases,the composition of coalbed methane and its classification were analyzed,.infuence factors of biogenic coalbed methane composititn were summarized,the problems and research directions were pointed.The results show that there are few difference in gas composition between biogas and thermal gas,and significant differences in stable isotope compositon.The biogenic coalbed gas can be comprehensive reoongited by the stable isotope composition characteristics and the gas related indexes.The biogas composition characterisics not only controlled by the aerogenic parent materials environmental water,but also infuenced by the anaerobic microbial population and enzyme activity. ue to multisource oarbon parent materials,the process of the biogenic coalbed methane and its intermediate materials should be further studied; combined with the gases characteristics of bioconverting coal to methane,the CD-diagram for biogenic coalbed methane classification should be modfied orland rebuilded.