A fully coupled fluid flow and geomechanics model is proposed for ECBM and CO2 underground storage with consideration of multi-component multi-process transportation in porous media to capture the complicated geomechanical effects, and the corresponding numerical solver is developed by the fully implicit finite difference method. The obvious difference of permeability and production index predication between the fully coupled model and empirical/analytical model is investigated, and the irrationality on assumptions of constant overburden pressure and universal axial strain adopted by the analytical models is judged, which verifies the accuracy and effectiveness of the fully coupled model. The model proposed can more accurately capture the fully coupling effects of geomechanics and fluid flow and multi-component multi-process migration in coal seam, which can provide better CBM production prediction.