The traditional chemotherapy using single agent may suffer from serious drawbacks, particularly dose-limiting toxicity and relatively low antitumor efficacy, which can lead to failure of chemotherapy. Co-delivery of two or more therapeutic drugs in nanotechnology is a potential strategy to generate synergistic anticancer effects and reduce individual drug-related toxicity, but explosive release of each drug from multi-drug loaded nanoparticles has been a distinct obstacle. In this study, a novel amphiphilic and biodegradable triblock copolymer, named MPEG-b-norbornene functional PLA-b-P(alpha-BrCL), was constructed to covalently conjugate dual anticancer drugs, i.e., doxorubicin (DOX) and paclitaxel (PTX). The resultant P-PTX-DOX prodrugs were confirmed by H-1 NMR and HPLC. By adjusting the length of PLA and PCL, it was shown that this polymer could carry relatively sufficient amount of both drugs (12.1 wt% of PTX and 15.8 wt% of DOX, respectively). Moreover, the drug release profile of P-PTX-DOX in vitro was also analyzed, which showed the desired drug release in a sustained manner. Cytotoxicity study indicated synergistic effects of P-PTX-DOX self-assembled micelles in suppression of proliferation of A549 cancer cells. In summary, a novel polyester-based copolymer was developed to covalently conjugate dual-drug, which exhibited controlled drug release behavior and synergistic anti-cancer efficacy in vitro.