The stability of the authors' self-formulated Ftorafur liposome was studied by the classical isothermal method at 60, 70 & 80℃. The particle size distribution of the particulates and the rate of their coalescence were determined by using the Coulter counter. It was shown that the change of particle size of Ftorafur liposome was a first-order reaction. The rate equation and the activation energy of coalescence and the kinetic constant of coalescence at room temperature were derived. The particle size distribution, appearance and homogeneity changed just slightly after storage at room temperature and in refrigerator (5℃) for 30 months, respectively. Drug enclosed within liposome leaked out about 3.8 % after storage for 3 months at 37℃ (?0.1℃). The above results indicate that the Ftorafur liposome is rather stable.