The invention relates to a method for sampling a special organic gas in a flue gas. The method comprises the following steps: allowing the flue gas to enter through the inner tube of a sleeve from the inlet of a sampling gun, adjusting the temperature, intercepting particles by a filter cylinder, condensing the flue gas by a condensation device, allowing the obtained condensate liquid into a cooling and liquid removing bottle, trapping the cooled and dried gas by a trapping bottle to remove dioxin substances, further collecting by a washing bottle, and allowing the gas to go through a dryer, a gas flow meter, a thermometer and a sampling pump to complete the whole sampling process. A whole flue gas sampling pipeline adopting a full glass structure has the advantages of corrosion resistance, no chemical reaction, convenient cleaning, and prevention of the loss caused by the adsorption or contamination of the acquired sample by the wall surface of a tube wall utensil; the jacket glass sampling gun can heat or cool the acquired flue gas by hot or cold air entering through an external layer; the condensate liquid collection bottle having scales can rapidly judge whether there is severe gas leakage in the sampling process or not; and the flue gas is cooled, condensed, and dehydrated, and then adsorbs a sampling agent to guarantee a high sampling efficiency.