Cholesterol-PEG-Thiol (CLS-PEG-SH) is a heterobifunctional PEG reagent containing a thiol group, which has good water solubility, and PEG cholesterol derivatives can be used to prepare targeted liposomes to improve the encapsulation of drugs cycle time, protected amines can be regenerated under mildly acidic conditions. The thiol moiety reacts with maleimide to form a stable thioether linkage.