Intracellular, reduction-responsive, amphiphilic, copolymer micelles with cancer cell specificity were developed. The copolymer was prepared with controlled molecular weight and functionalities using a double-headed initiator consisting of a disulfide linkage and folic acid targeting unit. The polymer could self-assemble into spherical micelles, which were stable under physiological conditions. Anticancer drug doxorubicin (DOX) was encapsulated into the micelles during the micellization and then released rapidly into the environment under the stimulus of intracellular reducing agent glutathione. Flow cytometry and confocal laser scanning microscopy observations further indicated that DOX was successfully released from the internalized micelles into the cytoplasm, inducing apoptosis and cell death. The potential of the present copolymer micelles for application as anticancer drug carriers for targeted cancer therapy is promising.