OBJECTIVE:To prepare Coenzyme Q10 long-circulating liposomes,establish the determination method of content and entrapment efficiency,and prepare it into lyophilized preparation to improve its stability. METHODS:Coenzyme Q10 long-cir-culating liposomes were prepared by film dispersion method. Particle size and Zeta potential of liposomes were determined,and HPLC assay was used to determine the content of coenzyme Q10. Free drugs and liposomes were separated using protamine aggre-gation method,and the encapsulation efficiency was calculated. Lyophilized preparation was prepared by coenzyme Q10 long-circu-lating liposomes,and the changes of content and encapsulation efficiency of drugs were determined 0,30 and 90 days after lyophi-lization. RESULTS:The liposomes were homogeneous in size with mean diameter of(166.0±5.3)nm and Zeta potential of(-22.2± 1.4)mV. Average content(the percentage of content accounted for labeled amount)and entrapment efficiency of 3 batches of sam-ple were 98.2%(RSD=2.8%) and 93.2%(RSD=4.6%),respectively. Compared with 0 d after lyophilization,coenzyme Q10 long-circulating liposomes had no obvious change in the content and encapsulation efficiency 90 d after lyophilization. CONCLU-SIONS:Coenzyme Q10 long-circulating liposomes with high quality and entrapment efficiency and lyophilized preparation being stored stably for 90 d have been prepared successfully.