Abstract: AimTo prepare 8-chloro-adenosine (8-Cl-A)long circulation liposomes with high entrapped efficiency and prolonged action-time of 8-Cl-Ain vivo. MethodsTo prepare 8-Cl-A long circulation liposomes of nanometer size by improved multiple emulsion. The entrapped efficiency, size and size distribution of 8-Cl-A long circulation liposomes were determined, and its pharmacokinetics in rats was evaluated. ResultsThe entrapped efficiency of 8-Cl-A long circulation liposomes was 62.70％ and mean diameter of the liposomes was 79.9 nm. The pharmacokinetics studies indicated that 8-Cl-A long circulation liposomes showed higher drug concentration and larger AUC values than that of 8-Cl-A after iv to rats. Conclusion8-Cl-A long circulation liposomes could prolong the action-time of 8-Cl-Ain vivo.