A series of fluorescent cellulose derivatives (AC-AET-DMANMs) with different degrees of substitution (DS) were successfully prepared. First, allyl cellulose (AC) was synthesized from cellulose in NaOH/urea aqueous solution, and then 2-aminoethanethiol (AET) was introduced onto the cellulose backbone via a thiol–ene click reaction. Finally, the fluorescent groups were introduced by the reaction of the AET-modified AC with 4-dimethylamine-1,8-naphthalic anhydride (DMANA). The structure and fluorescent properties of AC-AET-DMANMs were characterized by elemental analysis and FT-IR, 1H NMR, UV–vis, and fluorescence spectroscopy. AC-AET-DMANM with lower DSDMANM (referring to the DS of naphthalimide groups, ≤0.25) was soluble in DMSO. AC-AET-DMANM of DSDMANM ≤ 0.09 displayed stable fluorescence in DMSO and even in the solid state. The emission of AC-AET-DMANM in DMSO quantitatively and sensitively responded to 2,4,6-trinitrophenol (TNP) and 2,4-dinitrophenylhydrazine (DNH) by fluorescence quenching, and the limi...