Nano drug delivery systems have made significant progress in delivering anticancer drugs camptothecin (CPT). However, many challenges for CPT delivery remain, including low drug loading efficiency, premature drug leakage, and poor cellular internalization. Herein, we report a novel dual-sensitive polypeptide-based micelle with remarkably high drug loading of CPT for cancer therapy. This self-assembled micelle possesses the following essential components for CPT: (1) pH-sensitive PEG (OHC-PEG-CHO) for prolonging blood circulation and allowing biocompatibility by shielding the cationic micelles, which can be detached under the tumor acidic microenvironment and facilitates the cellular uptake; (2) polypeptide polylysine-polyphenylalanine (PKF) synthesized via ring-opening polymerization for micelle formation and CPT analogue loading; (3) dimeric CPT (DCPT) with redox-sensitive linker for increasing CPT loading and ensuring drug release at tumor sites. Interestingly, the linear-like morphology of PEG-PKF/DCPT micelles was able to enhance their cellular internalization when compared with the spherical blank PKF micelles. Also, the anticancer efficacy of DCPT against lung cancer cells was significantly improved by the micelle formation. In conclusion, this work provides a promising strategy facilitating the safety and effective application of CPT in cancer therapy.