A conjugate of water soluble polymer-amino acid oligopeptide-drug of Formula (I) below and a pharmaceutical composition comprising the conjugate are provided. In the conjugate, P is a water soluble polymer X is a linking group, wherein the linking group links P and A1 each of A1, A2 and A3 is independently same or different amino acid residue or amino acid analogue residue each of D1 and D2 is independently same or different drug molecule residue a is 0 or 1 b is an integer of 2-12 c is an integer of 0-7 d is 0 or 1. The conjugate could improve drug load capacity, water solubility, stability and activity of the drug.
