The present invention relates to an new type amphiphilic block copolymer and preparation method thereof, and a micellar drug-loading system formed by the copolymer with an antitumor drug. The amphiphilic block copolymer comprises an amphiphilic chain segment and a hydrophobic chain segment, wherein the end-group of the hydrophobic chain segment is blocked with a hydrophobic group. The amphiphilic block copolymer of the present invention employs a polyethylene glycol monoethylether (or polyethylene glycol)-polyester block copolymer with a recognized safety as a base material and the end-hydroxy of the polyester chain segment is modified with a hydrophobic group, which not only improves the compatibility of the drug molecule with the hydrophobic chain segment of the block copolymer and increases the force therebetween, but also provides a bigger space for accommodating the drug molecule； the prepared micelle can more effectively confine the drug molecule in the core of the micelle so that the drug molecule does not dissolve easily, thus the drug-loading micelle with high stability is obtained.
