Copolymers as a kind of drug delivery carrier always lack targeting efficiency. So a peptide conjugated to a drug delivery system has attracted much attention for tumor-targeted nanomedicine. Thus, we here report a conjugation compound consisting of a copolymer (PEG-b-PLL) and a peptide (Cys-Ile-Gln-Pro-Phe-Tyr-Pro, CP7). For receptor-mediated endocytosis by this peptide, the CP7-PEG-b-PLL conjugation significantly enhanced the chemotherapeutic efficacy as a potent nanocarrier compared with free DOX. The CP7-PEG-b-PLL exhibited excellent pharmacokinetic behavior via a radioactive iodine-131 (I) tracing method. With this, the CP7-PEG-b-PLL/DOX system showed better tumor growth inhibition when studied on A549 cell lines and subcutaneous tumor models, but with less toxicity than free DOX. All these results suggest that the CP7-modified drug cationic micelles could represent a novel platform for successful drug delivery toward VEGFR3-overexpressed tumors.