pH-Sensitive doxorubicin conjugated polymeric micelles entrapped with near infrared (NIR) photosensitizer BODIPY (which works as an imaging agent at the same time) were designed and synthesized by ring opening polymerization of N-carboxyanhydride with mPEG-NH₂ as the initiator, following reaction with doxorubicin to form the hydrazone-bond linker for pH responsiveness. Then the NIR dye (BODIPY) was loaded in the micelles for both bioimaging and photodynamic therapy (PDT). A significant cytotoxicity of NIR imaging-guided combined PDT and chemotherapy could be found by MTT assays, which was also confirmed with a fluorescence microscope, indicating a new kind of polymeric nanoparticle for potential theranostic treatment of cancers. In addition, the energy density of the laser for the PDT is extremely low.