Abstract: In the present paper, the relationship between physico-chemical properties of lecithin and encapsulation ratio of methotrexate (MTX) in liposome was studied. For two kinds of lecithin (egg lecithin and soybean lecithin) after storage for different length of times, their oxidation index, iodine value, ultraviolet absorption and thin-layer chromatography were examined. Using double emulsify evaporation method, MTX-liposomes were prepared from lecithin of different oxidation index and their encapsulation ratio of MTX were determined. In our experiment, it is shown that encapsulation ratio of MTX-liposome decreased with increasing oxidation index and iodine value of lecithin. After a long time of storage, both oxidation index and iodine value of lecithin increased and thin-layer chromatograms showed non-homogeneity. The results suggest that using lecithin With oxidation index below 0.2, iodine value about 60 and homogeneous thin layer chromatography a higher encapsulation ratio of MTX-liposome was obtained.