Forsythia suspensa Vahl (Oleaceae) is an important original plant in traditional Chinese medicine. The air-dried fruits of Forsythia suspensa have long been used to relieve respiratory symptoms. Phillyrin is one of the main chemical constituent of Forsythia suspensa. A clear understanding of the metabolism of phillyrin is very important in rational clinical use and pharmacological research. In this study, the metabolism of phillyrin in rat was investigated for the first time using an ultra-high-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) method. Bile, urine and feces were collected from rats after single-dose (10 mg/kg) orally administered phillyrin. Liquid-liquid extraction and ultrasonic extraction were used to prepare samples. UPLC-Q-TOF-MS analysis of the phillyrin samples showed that phillyrin was converted to a major metabolite, M26, which underwent deglucosidation, further dehydration and desaturation. A total of 34 metabolites were detected including 30 phase I and four phase II metabolites. The conjugation types and structure skeletons of the metabolites were preliminarily determined. Moreover, 28 new metabolites were reported for the first time. The main biotransformation route of phillyrin was identified as hydrolysis, oxidation and sulfation. These findings enhance our understanding of the metabolism and the real active structures of phillyrin. Copyright © 2015 John Wiley & Sons, Ltd.