The invention provides a fluorescent probe for detecting the polarity of a lipid droplet. The chemical name is 3-(4-(2,2-dicyanylvinyl)phenyl)-9-ethylcarbazole, and the structural formula is as shownin the specification. Due to the intramolecular distorted electron transfer effect (TICT) of the probe, a good response to solvent polarity is achieved. The fluorescent probe of the invention is electrically neutral, and can be well positioned in lipid droplets in cells. The probe can be accurately located in lipid droplets, has high sensitivity, good optical stability and specific response to polarity, and achieves detection of polarity of lipid droplets in cells. A method for synthesizing the probe has the advantages of simple steps, convenient purification and high yield.