Abstract: According to the actual condition of 103 working face, using the methods of theoretical analysis and field measurement, we analyze the emission characteristics and the volume fraction of coal seam gas at fully mechanized working face, and anlyze the relationship between gas emission amount and day advancing amount, yield, wind amount, mining processes, extraction volume, mine pressure. Research shows that gas concentration increases from the intake to the return air roadway along the tendency, but different positions increase differently; gas concentration presents trend of high, relatively high, low, relatively high, high from coal wall to support tail of goaf; there is a gas lowest between coal wall and goaf; goaf gas presents periodic variation trend from small to large with periodic roof caving, and then changes from big to small.