Abstract: Photodynamic therapy (PDT) is one of the new approaches for cancer treatment with high efficacy. However, applications of current photosensitizers are restricted to skin and superficial tumor due to poor in vivo targeting ability, poor water solubility and short wavelength excitement, which limits penetration therefore thera peutic depth. Here, a biodegradable polymeric micelle, methoxy poly(ethylene glycol)-polylactide copolymer (mPEG-PDLLA), is employed as drug delivery system to co-encapsulate strong two-photon absorption compound (L_TPA) and photosensitizers. This delivery system is designed to target tumor passively, resulting in near infrared light with an approximately 808 nm wavelength becoming able to indirectly excite photosensitizers through fluores cence resonance energy transfer. Tumor cells and microvessels could be damaged by the generated singlet oxygen. The average size of drug loaded micelles was approximately 55 nm and showed a spherical shape. Both com pounds could be released simultaneously from micelles under either weak acid and neutral pH conditions. Reactive oxygen species was produced intracellularly during two-photon PDT process and induced cell apoptosis/necrosis, which was quantified by Annexin-V/FITC assays. Time-dependent ex vivo organ distribution and in vivo anticancer efficacy results suggested that the drug carriers could accumulate in tumors and suppress tumor growth by twophoton PDT. All animals experiments were performed in line with national regulations and approved by the Animal Experiments Ethical Committee of College of Pharmaceutical Sciences, Southwest University. In summary, we have employed two-photon PDT for breast cancer treatment successfully in a mouse model and have demonstrated the significance of delivery system in such therapeutics.