The present invention relates to a coal liquefaction device online analyzing sample pretreatment system. The present invention uses a secondary treatment method. A first stage filter comprises a T-shaped filter, a reducing valve and a safety valve. A second stage filter comprises a compressor, a bulk tank and a drier filter in order. The sample inlet of the compressor is connected with the first stage filter. The outlet of the compressor is connected with the inlet of the drier filter through a valve. The water outlet of the compressor is connected with the inlet of the bulk tank. The water outlet is arranged on the bulk tank. A dew point intelligent monitoring and control device comprises automatic valves which are respectively arranged on the sample inlet of a tee filter and the sample inlet pipeline of the drier filter, and a dew point intelligent monitoring and control machine which is arranged on the sample outlet of the compressor. The dew point intelligent monitoring and controlmachine is used for monitoring the water content in the sample outlet and controlling the interruption of the automatic valves. The coal liquefaction sample is treated by two stage cooling, removingwater and dust removal filtration. So the temperature, the water content and the dust content of the sample are ensured to meet the requirement before entering an analytical instrument.