Permeability tests of type I to V coal from Jiaozuo coalfield are carried out to study the gas permeability difference of coals with different structures. The experimental results show that the relation curve of permeability to different coal structures show normal distribution, and the value of permeability first increases quickly and then decreases sharply. Type II coal’s permeability is the maximum and that of type V is the minimum. There is little difference of perm abilities of type I, type IV and type V. The concepts of variation coefficient of permeability and permeability ratio are brought in to evaluate the heterogeneity and anisotropy of No.21 coal seam. It found both of them are high, however, the homogeneity of a single type structure coal is good. Mechanisms of gas sub region and banding, gas emission, gas outburst of gas bearing coal are explained by the permeability differences. Permeability changes are the direct result of pore fracture development and the major controlling factor of gas distribution, gas emission and coal and gas outburst.