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(α-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 1H 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.