Abstract: Basic structure and working principle of dry-gas seal are introduced.The paper provides the technical requirements on gas quality filtering unit, pressure adjusting/flowrate control unit, monitoring unit of leakage volume and supply unit of insulating air about dry-gas seal used in West-to-East Gas Transmission Pipeline.Cause analysis is made on invalided dry-gas seals in Hongliu Compressor Station, Shandan Compressor Station and Hami Compressor Station; replacing pre-filter with GCU, failure issue of dry-gas seal of compressor is solved; daily care requirements on dry-gas seal's running condition of compressor are put forward.