Photodynamic therapy suffers from poor tumor selectivity and poor therapeutical efficacy. In this paper, an amphiphilic chimeric peptide is fabricated to realize sequential acidity-responsive tumor-targeted transport of photosensitizer and in situ photodynamic therapy in nuclei. In vitro studies demonstrate that the acidic tumor microenvironment successfully sheds the mask of cationic nuclear localization sequence (NLS) of the negatively charged chimeric peptide. This charge reversal remarkably accelerates cellular uptake of chimeric peptide in tumor cells and maximizes the photodynamic therapeutical efficacy in nuclei. Most importantly, direct disguise of the biofunctional NLS sequence decreases the complexity and increases the performance of the chimeric peptide further by achieving long blood retention time, specific tumor accumulation, minimal side effects, and efficient antitumor therapy in vivo.