Adriamycin (ADR) was selected as a model drug to evaluate the potential applications of polylactide/poly(ethylene glycol)/polylactide (PLA/PEG/PLA) micelles as drug carriers in parenteral delivery systems. The PLA/PEG/PLA triblock copolymer micelles were characterized by dynamic light scattering and transmission electron microscopy. It was found that the micelle size increased with the increasing of the PLA chain length. The average size of ADR-loaded micelles was 143.2 nm. The histogram analysis showed that the ADR-loaded micelles possessed a narrow unimodal size distribution. The ADR loading contents of the micelles and ADR entrapment efficiency were dependent on the PLA chain length and PEG chain length in the copolymer. They increased with the increase of the PLA chain length, but the PEG chain length was identical and decreased with the increase of the PEG chain length; the length of the PLA block was similar. The initial amount of ADR also influenced the drug contents and entrapment efficiency (i.e., the more the initial amount added, the more the drug contents and the higher encapsulation efficiency). The drug release experiments indicated that the ADR-loaded micelles possessed sustained release characteristics.