Bioassay-guided fractionation of extracts from Fructus Gardeniae led to analysis of its bioactive natural products. After infection by influenza virus strain A/FM/1/47-MA in vivo, antiviral activity of the extracts were investigated. The target fraction was orally administered to rats and blood was collected. High-performance liquid chromatography coupled with photo diode array detector and electrospray ion trap multiple-stage tandem mass spectrometry was applied to screen the compounds absorbed into the blood. A structural characterization based on the retention time, ultraviolet spectra, parent ions and fragmentation ions was performed. Thirteen compounds were confirmed or tentatively identified. This provides an accurate profile of the composition of bioactive compounds responsible for the anti-influenza properties.