Abstract: According to the importance of permeability change in enhancing coalbed methane ( ECBM) recovery, the paper studied the permeability change laws al ong with time and its improved effects induced by the reaction CO 2 injection and minerals in coal. The results showed that the permeability increased at first and then t urned up to decrease along with CO 2 injection, the maximum value of permeability change appear after 1. 75 months. The improvement of permeability was not obviou S to too small or too big initial seam permeability, while the medium seam permeability( 0.3036~ 3.099 0) x 10- 3μm2improvement was the best. Finally, the paper bu ilt three kinds relationship model ( R- R type、|- R type、|- I type) between permeability and porosity of seam by analyzing the change relationship between permeabilit y and porosity with time to different coal samples. Accroding to analysis results, |- | type was the best to coalbed methane development.