To increase the stability and bioavailability of antisense oligodeoxynucleotides, and to avoid being destroyed by the lysosomes, pH-sensitive prelip-osomes were preparaed by using of dehydration-rehydration, ultrasonication, extrusion, lyophilization methods. The effects of different variables on the preparation of pH-sensitive preliposomes were studied. The optimized preparation conditions of pH-sensitive preliposomes were acquired through orthogonal test. The experiment revealed that the pH-sensitive liposome was regular in its morphology with a mean diameter of 22.7 nm. The mean entrapment efficiency of antisense oligodeoxynucleotides of three batches was 68.3%. The release properties could be expressed by the following equation: Q=1.8382－2.5186×10^－2T(r=0.9913).Based upon the various assays used to measure the entrapment efficiency and diameter of pH-sensitive liposomes, it was concluded that the entrapment of antisense oligodeoxynucleotides by pH-sensitive preliposomes was effective.