The present invention discloses a fluorescent compound having a sensing ability to aniline and o-toluidine, a preparation method thereof, a preparation method and application of a fluorescent sensing film. The compound contains a naphthalenediimide (NDI) unit, two alkynyl aniline conjugate fragments and two long alkyl chain fragments; compared with perylene anhydride (PDI), naphthalenediimide (NDI) has better solubility, rich photophysical property, good photochemical stability and strong π-π stacking effect; these building units make the prepared fluorescent compound have supramolecular characteristics and more abundant gelling behavior and assembly behavior. Therefore, the sensing film prepared with the fluorescent compound is controllable in the microstructure, good in stability, high in sensitivity, long in service life and able to be repeatedly used. The present invention achieves the sensitive detection of aniline, and more importantly, the detection is completely reversible, so as to lay the solid foundation for the realization of aniline fluorescence sensor.