A synchronous solid-surface fluorimetry (S-SSF) method combined with an optical fiber and a fluorescence spectrophotometer was established for in situ determination of anthracene and pyrene adsorbed onto Kandelia candel (L.) Druce and Aegiceras corniculatum (L.) Blanco leaves as single components and in mixture. Using the established approach, the linear dynamic ranges and detection limits for determination of anthracene and pyrene adsorbed onto the leaves of two mangrove species as single components and in mixture were investigated. The relative standard deviations were all less than 10% (n — 6), and the experimental recoveries with S-SSF of adsorbed anthracene and pyrene on K. candel and A. corniculatum leaves as single components and in mixture were between 82.9% and 116.5%. Furthermore, with the established method, the spectroscopic behavior of anthracene adsorbed on the living K. candel leaves were studied in situ, and gas chromatography-mass spectrometry was also used to verify the accuracy of the S-SSF approach. The results demonstrated that in a certain period of exposure time to anthracene, the trends for quantity of adsorbed anthracene on the upper side of living K. candel leaves determined by the two methods were similar. The S-SSF approach proved to be a simple, fast, and easy method, without the necessity of sample pretreatment with a large amount of organic solvent. Therefore, the S-SSF method has great potential for use in the field, and experimental conditions were further optimized and the sensitivity of the method improved.