The invention relates to a fluorescence sensor for rapid detection of explosives and a preparation method thereof, and a method for rapid detection of explosives, wherein the fluorescence sensor and the method especially have high selectivity and sensitivity in trace detection of picric acid. The fluorescence sensor is a solution having a concentration of 1*10<-4> to 1*10<-6> mol/L and prepared by dissolving a graphene composite material in a solvent. The graphene composite material comprises graphene and a polymer as shown in a formula I which is described in the specification, wherein the polymer modifies graphene in a non-covalent bond manner via in-situ reduction of graphene oxide. When the concentration of picric acid is in a range of 1.3*10<-3> to 3.3 ppm, reduction in the fluorescence intensity of the fluorescence sensor is in linear relation with the concentration of a nitro-containing explosive, and quantitative determination can be realized. The fluorescence sensor has good fluorescence characteristics and AIE effect, can realize qualitative and quantitative determination of trace picric acid and is high in sensitivity and low in cost. The method for rapid detection of explosives is simple to operate and has good application prospects.