The diblock copolymers based on PBLG and PEO (GE) were synthesized and characterized. Nanoparticles showed spherical shape from the observations of TEM and approved core-shell structure. Drug contents were increased with use of higher initial drug concentration and higher Mw of GE. Nifedipine (NFD) release rate was slower in longer PBLG chain length and higher NFD contents than short PBLG chain length and lower drug contents of NFD due to the hydrophobic interaction between PBLG domain and NFD.