In order to provide the basis for differentiating PAHs and test PAHs in environment, snchronous fluorescence spectra of ten kinds of standards PAHs(naphthalene, fluorine, anthracene, phenanthrene, pyrene, acenaphthene, chrysene, 1,2benzo［A］ anthracene, benzo［k］ fluoranthene, benzophenanthrene) and their mixed solutions(anthracene/ naphthalene/ fluorine, acenaphthene/ fluoranthene/phenanthrene and pyrene /1,2benzo［A］ anthracene/benzo［k］ fluoranthene/benzophenanthrene)are measured. The differences of the excitation and emission wavelength Δλ are obtained when the characteristic peaks are the most evident. Based on above results, the composites of the three kinds mixed solutions are identified by synchronous fluorescence spectra. The results show that it is easy to distinguish anthracene, naphthalene and fluorine when Δλ equals 3 nm.For acenaphthene, pyrene and phenanthrene, Δλ equals 3 nm or 10 nm,the three composites can be differentiated. It is relative simple when Δλ equals 10nm. For the mixed solution of chrysene, 1,2benzo［A］ anthracene, benzo［k］ fluoranthene and benzophenanthrene, it is the best when Δλ equals 5 nm, but only chrysene, 1,2benzo［A］ anthracene and benzo［k］ fluoranthene could be identified, benzophenanthrene is indefinite.