A fluorescent probe with high selectivity and sensitivity was synthesized for hydrazine determination in physioligical condition(pH 7.4) based on coumarin dyes.Structure of the probe was characterized by nuclear magnetic resonnce and high resolution mass spectrometry.A strong fluorescence imine coumarin was generated by using hydrazine attacking 4-butyrate to release phenolic oxygen anion and produce molecular inner reaction.With the addition of hydrazine(0-100 μmol/L)，the fluorescence intensity of the probe displayed a remarked enhancement(55 fold) in green spectral region(502 nm).The probe could be used to detect low concentration of hydrazine，with a detection limit of 1.7×10-7 mol/L.Compared with the other anions and nuclear reagents，this probe showed higher selectivity and sensitivity to recognize hydrazine.More importantly，the probe was successfully implemented to detect hydrazine in living cells，which proved that the hydrazine fluorescent probe has a potential capability in cell imaging.