10-O-(N,N-dimethylaminoethyl)-ginkgolide B methanesulfonate (XQ-1H), a novel active derivative of ginkgolide B, is a platelet-activating factor antagonist which is being under clinical trial. Two unknown related impurities were observed in analysis of XQ-1H bulk drug. A scaling up preparative liquid chromatography (Prep LC) was used for isolation of the two impurities. Based on LC-MS/MS and nuclear magnetic resonance (NMR) spectra, they were characterized as 10-O-(N,N-dimethylaminoethyl)-11,12-seco-ginkgolide B (imp-1) and 10-O-(N,N-dimethylaminoethyl)-11,12,2,15-diseco-3,14-dehydroginkgolide B (imp-2), respectively. A reversed-phase liquid chromatography (RP-LC) was developed for simultaneous determination of XQ-1H as well as imp-1 and imp-2. Main variables that significantly influence the chromatographic procedure were optimized and efficient chromatographic separation was achieved on a CN column with mobile phase consisting of 5mM dipotassium hydrogen phosphate (pH 7.5) and methanol delivered in a gradient mode at the flow rate of 1.0mLmin(-1). The method was validated and found to be suitable to check the quality of bulk samples of XQ-1H at test concentration of 5.0mgmL(-1) for a 20microL injection volume.