Abstract: Dafosi Coal Field in Binchang Mining Area is rich in coalbed methane resources. The key factor of gas drainage is the difficulty of gas migration in coal seam, namely permeability. The coal seam permeability and its key control factors are analyzed by on-site sampling, laboratory samples preparation and coal samples seepage test system. The gas flow channel in the vertical bedding direction of the coal sample is less developed than the parallel bedding. The moisture enters the coal body and blocks the gas flow channel, which have more effect on the gas migration in the vertical bedding direction. And the permeability decreases significantly with the increase of moisture content of coal sample, which is not conducive to gas drainage.