Disclosed is a multi-arm targeting drug conjugate modified by a water-soluble polymer； the drug conjugate has the structural formula of (III). In formula (III), R is an organic core, POLY is a polymer, L is a multivalent linker, T is a targeting molecule, D is a camptothecin-based drug, and q is any integer between 3 and 8. The drug conjugate may improve the poor water solubility, high toxicity and low bioavailability of camptothecin-based drugs.
