Abstract: acording to the genesally low permeatility characteristics of the coal reservoir in the Rangal stata of Eowen Basin Australathe paper ad an indepthanlysis on th .flings n cracks of diferent seam and the seam macro heterogeneity affected to the permeability and analyzed the low permeabilily cause ofthe seamThe study showed that th crack ling of the sean ould be the major facor affected to the permea bility of the seam.Above the Rangal statathe iling would mainly be the clay 'ilings ofthe seam cracks and bll w the Rangal strat ,th flings would mainly be the carbonate illings of the seam cracks . 'he coal core test analysis andthe DST fest resuts showed that the bellvw seam permeabilit was far lower than the permeability of the above seam and there would be over two orders of magniudebetiween the two seam permeailities. n adition,the mineral contents and the longitudinal heterogeneity of the seam woult be the macro factors affected to the seam permeability, The igher mineral content was ,the lower horizontal permeability of the seam would be An interaction distrbution of the duain and clarain caused the ighverical heterogen eity and would seriously infuence the longtudinal permeatilty, The study helda that above the Rangalstata the seam pemeatility would be relativelyhigh and could be the key potential mining seam.