Unloading mining can effectively reduce geo-stress around coal seams and increase coal permeability, which results in the improvement of coal mine methane drainage and ensures the coal mining safety. Remote unloading mining is one of the several forms of unloading mining. To study coal mine methane drainage of these remote unloaded coal seams which are under the specific geologic conditions, we analyzed the characteristics of geostress-relief gas migration and the changes in permeability. A suitable mathematical model about coal permeability was established based on some existed theories. Comsol Multiphysics software was adopted to create different numerical simulation models that study coal mine methane drainage processes of original and remote unloaded coal seams. Situations of gas pressure change and daily gas drainage volume reveal that the gas extraction effect of coal seams affected by remote unloading mining is better than that of original coal seams. Besides, coal permeability affected by remote unloading mining and variations in permeability during geostress-relief gas extraction were compared and discussed. The above results indicate that remote unloading mining could effectively change the level of coal permeability and improve gas extraction amount. In addition, data of gas extraction amount obtained from numerical simulation were compared with that of field, and these two kinds of data are relatively consistent, which can demonstrate the effectiveness of the proposed mathematical model. Over the longer term, the mathematical model could be used to predict and evaluate variations in geostress-relief gas extraction levels.