Characteristic time-resolved fluorescence spectroscopy of polycyclic aromatic hydrocarbons were studied. Stimulated Raman scattering (SRS) was used to generate several excitation wavelengths, 289nm was selected as excitation source in this paper. Delay characterization and gate characterization were researched. According to the decay relationship between fluorescence intensity and delay time, fluorescence lifetime of phenanthrene, fluoranthene, fluorene, pyrene were obtained, which were 370, 327, 109, 1470 ns respectively. Different fluorescent substances have specific fluorescence spectral characteristics, the study of time-resolved fluorescence spectral of polycyclic aromatic hydrocarbons can provide the diagnosis basis for different polycyclic aromatic hydrocarbons in complex water environment.