As an emerging cancer therapy with high selectivity, minimally invasive and low side effects, photodynamic therapy (PDT) has become the focus of current researches. The breast cancer is a malignant tumor with the highest incidence in women. Thus, it is valuable for improving its treatment efficiency to construct efficient photosensitizer. To this end, we engineered a high stable near-infrared photosensitizer NPA-NH2 based on “step by step” strategy. By modifying the optically tunable amino group of NPA-NH2, a peroxynitrite (ONOO-) activated NPA-ONOO- theranostic agent with a new trifluoromethylsulfonamide recognization site was designed and synthesized. It possessed a good singlet oxygen-generating ability after ONOO- activation under 660 nm light, and a high sensitivity (limit of detection: 0.038 μM) and selectivity respond toward ONOO- in buffer solution. The theranostic agent was able to specially monitor ONOO- in tumor cells. Furthermore, we have succeeded in applying the NPA-ONOO- for efficient and precise photodynamic therapy of breast cancer cells and tumors in vivo. This work provides a new way for the design of highly stable photosensitizers and a reliable tool for effective treatment of breast tumors.