Abstract: To investigate the absorption mechanism of diammonium glycyrrhizinate (GL) for oral use in rat intestine as well as the effect of phospholipids on GL and its metabolite glycyrrhetic acid (GA), in situ single pass intestinal perfusion model and the rat single-pass intestinal perfusion with mesenteric cannulation model were used and the concentrations of GL and GA in perfusate and blood were determined by HPLC. The apparent permeability values (P_app) of GA with or without phospholipids are 7.98 and 5.73 cm·min^-1, respectively, whereas the permeability of GL had no significant statistical difference. The results showed that phospholipids can increase the absorption extent and speed of GA. This action can be used in the research and development of the new drugs of the glycyrrhiza.