Abstract: OBJECTIVE To objective the binding and degradation of TAP photosensitizerZnPc(TAP) with breast cancer cell DNA. METHODS TAP singlet oxygen production and its types were detected by probe method. The interaction between TAP photosensitizer and DNA of breast cancer cells was studied by UV spectroscopy and its binding constants were calculated. The degradation of TAP on DNA of breast cancer cells was explored and analyzed intracellular and extracellular by gel electrophoresis, imaging and nucleic acid detection. RESULTS It was proved that TAP photosensitizer had good UV absorption and fluorescence spectrum properties, Its production of singlet oxygen was abundant. It could produce significant hydrogen and oxygen radicals to achieve photodynamic effect. TAP photosensitizer had strong interaction with breast cancer cell line DNA with a binding constant(Kdu) as 3.72×10⁶. Both intracellular and extracellular photodynamic experiments demonstrated that TAP photosensitizer could degrade DNA in breast cancer cell line, and its degradation was positively correlated with the concentration of photosensitizer. CONCLUSION TAP photosensitizer has significant photodynamic degradation effect on breast cancer cell DNA, which is helpful to promote the application of TAP photosensitizer in cancer DNA and provide reference value for the treatment of breast cancer metastasis and recurrence.