A method of two-dimensional liquid chromatography with online enrichment was established for the determination of trace ginkgolic acids in Ginkgo biloba extract（EGB） and their preparations.The liquid chromatography system was composed of two LC pumps,an UV detector,a manual sampling valve,a switching valve and two columns.The ginkgolic acids were enriched on the first dimensional column of ZORBAX Eclipse Plus-C18（2.1 mm×12.5 mm,5 μm） using a methanol-water-trifluoroacetic acid mixture（80∶20∶0.01） as mobile phase at a flow rate of 0.25 mL/min,then separated on the second dimensional column of ZORBAX Eclipse Plus-C18（2.1 mm×150 mm,5 μm） using a methanol-water-trifluoroacetic acid mixture（90∶10∶0.01） as mobile phase at a flow rate of 0.25 mL/min,finally detected with a UV detector at 310 nm.The effects of sample solvent and sample volume on the enrichment were investigated.When the sample solvent was consistent with the first dimension mobile phase,the enrichment on 300 μL sample could be achieved.There existed good linear responses for 5 kinds of ginkgolic acids in the range of 0.200-100.0 mg/kg,with correlation coefficients greater than 0.998 and detection limits of 0.02-0.06 mg/kg.The recoveries at two spiked levels of 5 mg/kg and 10 mg/kg were between 94.0% and 101.3% with relative standard deviations not more than 5.0%.