Abstract: Particulate matter such as dust and free water is often entrained into coalbed methane (CBM),which affects the safety of the operation in gathering system. The on-line detection method for particulate matter was used to find out the distribution characteristic of the impurity in gas gathering system. Dust concentration and particle size distribution, free water and water vapor concentration can be obtained at the gathering nodes,including wellhead,manifold,gas gathering station and central treatment plant. It was found that the content of liquid impurities was large,and the impu- rities deposition phenomenon was obtained. The impurities were also captured for chemical composition analysis,which could affect the composition of solid impurities and the property of liquid impurities. Particulate matters were obvious different before and after the compressor. To deal with the problems of separation equipment,the improvement measure of existing filter element was proposed. The test in the laboratory and field proved that the improved element had lower resistance and higher efficiency. The improved filter element could effectively reduce the operation cost and is suitable for the CBM system with a low pressure characteristic.