Abstract: Taking Hancheng coal mining area in Ordos basin as an example, this paper presents the isothermal adsorption experiment of N2 and CO2 to make proper characterization of coalbed specific surface area. The correlation analysis between Langmuir volume from coalbed methane isothermal adsorption and specific surface area from N2/CO2 gas adsorption indicates a positive correlation between coalbed methane adsorption capacity and CO2 SD?R, and a weak correlation between coalbed methane adsorption capacity and N2 SBET. According to the coalbed CO2 adsorption data, coalbed contains a great number of micropores with diameter of 0.5~1.0 nm by DET model calculation approach, while for N2 adsorption data, it has poor effective micropores, which shows that CO2 SD?R is more representative of the coalbed adsorption capacity than N2 SBET. So the coalbed is characterized by more developed micropores and they control adsorption capacity. It is suggested that the coalbed specific surface area should be characterized by CO2 SD?R