Abstract: Active carbon has some distinctive feature, such as small dimeter particle, light weight weight, high hardness and poor hydrophilicity. Therefore it is difficult to be woped out from the object it stuck. Up to now, hardly has been found the successful way of dealing with it at home. A new type of bag filter is studied. Comparison between membrance filter and needlefelt materials, concerning the loss of the obstruction, applicable area, cleaning period and so on are made based on experiments. A conclusion is drew:membrance filter material is better than needeflt.