Dynamic behavior of a fluorescent probe, a swallow-tailed perylene derivative (Spy-Hp) for detecting hydroperoxides was studied by fluorescence lifetime and transient absorption measurements. The MO calculations suggest the intramolecular charge transfer for Spy-Hp. The excited state lifetime of SpyHp is shorter than that of the oxidized form, which was caused by intramolecular fluorescence quenching. These results elucidate the mechanism of Spy-Hp for detecting hydroperoxides in biosamples.