Method for sampling flammable and explosive gas under negative pressure

The invention belongs to the analytic chemistry field, and concretely relates to a method or sampling flammable and explosive gas under negative pressure. The method comprises the following steps: 1)selecting an appropriate sampling point, inserting a sampling tube in a gas pipeline, sealing a sampling port; b)connecting an explosion-proof atmosphere sampling instrument and a sampling bottle, starting the explosion-proof atmosphere sampling instrument, setting the explosion-proof atmosphere sampling instrument with pressure less than pressure in the gas pipeline, connecting the sampling bottle and the gas pipeline, sampling; and c)after sampling, disconnecting the sampling bottle and the gas pipeline, then disconnecting the sampling bottle and the explosion-proof atmosphere sampling instrument, and turning off the explosion-proof atmosphere sampling instrument. In the invention, the appropriate sampling point is selected, the explosion-proof atmosphere sampling instrument is turned on, sampling is carried out, liquid in the pipeline or extraneous air in the gas pipeline canbe avoided, and risk during a sampling process can be reduced at maximum degree.