Abstract: Through reservoir geologic effect experiments of dry-coal samples and numerical simulation, the present paper studied dynamic variations in CBM reservoir physical properties and their negative influence on the CBM development. The results showed that variations in the CBM reservoir permeability were characteristic of a “U” form during the CBM development, the stress sensitivity was dominant at the beginning and the matrix shrinkage effect increased gradually as the development proceeded. The gas permeability decreased by 90% when the pressure increased from 2MPa to 10MPa, and the permeability could not recover completely even if the stress decreased. The numerical simulation by a P&M permeability model indicated that the permeability declined first and then ascended. When the pressure dropped to the critical point of desorption pressure (4.4MPa), the permeability decreased by 34%; then the permeability began to rebound to the initial value as the pressure decreased to 2.5MPa; finally the permeability increased by 2.8 times of the initial value as the pressure decreased to 0.7MPa. Moreover, a lower primary permeability and its reservoir geologic effect strongly influenced the deliverability of a CBM well, so the CBM production should be incessantly adjusted and optimized according to dynamic variations in the reservoir permeability.