Abstract: The present invention provides a half-life extension drug and a library thereof, and a preparation method and application thereof. Specifically, the present invention provides a drug library, comprising: (a) a drug unit; and (b) n half-life extension units, wherein the drug unit comprises a drug element portion and a first nucleic acid element portion connected to the drug element portion, and each half-life extension unit comprises a half-life extension element portion and a second nucleic acid element portion connected to the half-life extension element portion. Moreover, one first nucleic acid element portion of the drug unit and the second nucleic acid element portion of the at least one half-life extension unit may form a “drug unit-half-life extension unit” complex by forming a complementary base pairing structure, and n is a positive integer greater than or equal to 1.