A microdialysis on-line coupled to a reversed-phase liquid chromatography was investigated and applied for analyzing catechins in tea and tea drinks. Catechins in drink samples were diffused into the perfusate through a hollow fiber membrane and then on-line injected into the HPLC system. Catechins were separated with a C8 reversed column by gradient eluting using an acetonitrile/ phosphate buffer solution at pH 4.0, and monitored by a UV diode-array detector. Factors affecting the dialysis efficiency such as the conditions in perfusate and in the sample solution were evaluated. The proposed method provided a simple procedure for isolating catechins from tea and tea drink samples. The application was illustrated by the analysis of epicatechin, epicatechin gallate, epigallocatechin, and epigallocatechin gallate in tea drinks.