The invention relates to a preparation method of a fluorescent molecular probe for detecting fluoride ions in aqueous solutions through fluorescence enhancement and an application of the fluorescent molecular probe to detecting fluoride ions. The fluorescent molecular probe is prepared by protecting 1,4-diethyl-1,2,3,4-tetrahydro-7-hydroxyquinoxaline-6-aldehyde taken as a raw material with silane and then condensing the raw material and malononitrile. The fluorescent molecular probe is simple and convenient to synthesize, and reaction conditions are mild. The fluorescent molecular probe has the specific characteristics that the probe molecule has stable optical properties and higher synthetic yield; the probe molecule has high sensitivity of detection of fluoride ions in the aqueous solutions and low lower limit of detection, and the limit of detection is 5.4mu M; the response range is 0-1mM and the detection range is wide; the probe molecule has good selectivity and has no responses to anions, such as chloride ions, bromide ions, iodide ions, tetrabutylammonium cyanide, nitrates radicals, hydrosulfate radicals, perchlorate radicals, acetate radicals, thiocyanate radicals, azide radicals, cysteine, bovine serum albumin, carbonate radicals, sulfate radicals and reduced glutathione; the fluorescent molecular probe has practical application values in the fields of biochemistry, environmental sciences and the like.