The invention discloses a preparation method of a pyrene-containing conjugated polymer fluorescent sensing film, comprising the steps of tailoring a substrate, preparing lotion, preparing an activated substrate, preparing a pyrene-containing conjugated polymer, preparing a stock solution of the pyrene-containing conjugated polymer, and preparing the pyrene-containing conjugated polymer fluorescent sensing film. The fluorescent sensing film can be prepared by introducing a pyrene group into a conjugated fluorescent polymer main chain and coating the synthesized pyrene-containing conjugated polymer on the surface of the substrate; and the invention realizes the sensitive detection on solutions of nitryl aromatic explosives. The preparation method is simple and convenient for operation and has mild reaction condition. The prepared fluorescent sensing film has the advantages of favorable stability, long service life and high sensitivity, can be used for a sensor for detecting nitryl-containing aromatic compounds, or can be arranged on a detection instrument for detecting the nitryl-containing aromatic compounds by using the fluorescent principle. In addition, the fluorescent sensing films are subjected to nitryl aromatic chemical combination and are directly detected by using a fluorescent instrument.