To prepare lomustine-iohexol compound liposomes, and evaluate the properties, determine the entrapment efficiency. Liposomes were prepared by reverse evaporation method; orthogonal design was used to optimize the formulation. Free drugs and liposomes were separated using protamine aggregation method and entrapment efficiency was determined by HPLC. The optimal formula was as follows: soybean phospholipid 80, proportion of phospholipid and cholesterol was 2:1, lipid contents was 33 mg/ml ； protamine aggregation method can be well used to entrapment efficiency determination. The mean diameters of compound liposomes were 237.3nm, Zeta potentials were -43.9 mV, and the entrapment efficiency of lomustine and iohexol were 75% and 65%, respectively. The formulation and preparative method can be used to prepare compound liposomes with high entrapment efficiency; protamine aggregation was effective and rapid and can be used to determine the entrapment efficiency accurately.