The hydrophobic block of polymeric micelles formed by amphiphilic copolymers has no direct therapeutical effect, and the metabolites of these hydrophobic segments might lead to some unexpected side effects. Here the hydrophobic core of polymeric micelles is replaced by highly water-insoluble drugs themselves, forming a new micellar drug delivery system. By grafting hydrophobic drugs of paclitaxel (PTX) onto the surface of hydrophilic hyperbranched poly(ether-ester) (HPEE), we constructed an amphiphilic copolymer (HPEE-PTX). HPEE-PTX could self-assemble into micellar nanoparticles in aqueous solution with, tunable drug contents from 4.1 to 10.7%. Moreover, the hydrolysis of HPEE-PTX in serum resulted in the cumulative release of PTX. In vivo evaluation indicate that the dosage toleration PTX in mice had been improved greatly and HPEE-PTX micellar nanoparticles could be used as an efficient prodrug with satisfactory therapeutical effect. We believe that most of the lipophilic drugs could improve their character through this strategy.