Abstract: AIMTo study the entrapment efficiency of different drugs (mainly proteins and polypeptides) in liposomes prepared by a new method using saturated phospholipids at room temperature and the in vitro properties of obtained liposomes. METHODSThe liposomes was prepared by reverse phase evaporation in which a special adjunct was added. Urokinase and hirudin were fluorescene-labelled for determation of entrapment efficiency. The urokinase liposomes were used to observe the diameter distribution and the TEM photos; The leakage experiment of liposomes was done in PBS (phosphate buffered solution) and FCS (fatal calf serine). RESULTSThe adjunct of only 0.2 mg·mL^-1 and ultrasound time of only 1 min was enough to prepare liposomes at room temperature by saturated phospholipid; the liposomes were stable in storage, with the mean diameter under 100 nm and good shape; the entrapment efficiency was about 23% for hirudin and insulin, 65.44% for urokinase; the leaking rate of liposomes was slow either in PBS or in FCS at 37℃. CONCLUSIONThe preparation method was at mild conditions, gave stable products and was very stuitable for such drugs as proteins and polypeptides with high entrapment efficiency for high molecular proteins.