A fluorescent self-assembled monolayer film sensor with discriminatory power was specially designed and prepared by using pyrene as a reporting unit and a oligo(oxyethylene) unit as a hydrophilic spacer. The chemical attachment of pyrene moieties on the surface was verified by contact angle, XPS, UV-vis and fluorescence measurements. The fluorescence responses of the present film to nitroaromatic compounds (NACs) including picric acid, 2,4,6-trinitrotoluene, 2,4-dinitrotoluene, and nitrobenzene were measured. Significantly, the present film exhibits cross-reactive responses to different NACs, and the array of fluorescence variation at four specific wavelengths (peaks for pyrene's monomer emission and excimer emission) provides a distinct recognition pattern for each NAC. The results from principle component analysis reveal that the present film has discriminatory power to identify structurally similar NACs. Moreover, the present film exhibits a high sensitivity, selectivity and reversibility towards NACs, and provides great potential in instrumentation and miniaturization. The use of multiple signals of a single film sensor based on fluorophore's different aggregation states (e.g., pyrene's monomer, distorted excimer, and perfect excimer in the present work) instead of an array of sensor elements provides a novel strategy for developing discriminatory materials and remarkably simplifies the process of identifying similar chemicals.