The cationic photo-responsive polymeric micelles (mPEG-b-p(DEMA-co-MMA-CL)) with light-switchable cross-linker were designed and fabricated by atom transfer radical polymerization and quaternization. These micelles were well dispersed spherical with positive charge. The efficient release of encapsulated contents can be triggered by light irradiation. No significant toxicity was observed of copolymer and its photolysis residues at concentrations up to 250g/mL. The antitumor activity of camptothecin (CPT) in micelles demonstrated that light triggered the release of CPT, which dramatically improves the cytotoxicity after UV irradiation.