Paclitaxel-loaded methoxy poly (ethylene glycol )-b-poly (L-lactic acid) diblock copolymer nanoparticles (PMT) were prepared by a self-emulsification/solvent evaporation method. The PMT morphology, size and its distribution, and drug release in vitro were investigated by DLS, UV, TEM and HPLC. The results indicate that PMT show a spherical morphology with inner core and outer shell. The diameter (nm) of PMT increases with the increase of the drug-loaded amount. The initial burst release is not observed, the drug releasing rate in vitro is lower, and the accumulated release increases with the increase of replacement amout of the pH7. 4 medium. This study develops a new formulation for paclitaxel and provides an experimental basis for the intravenous administration of paclitaxel.