Abstract: Deactivated photosensitizer 5-4-N-(2,4-dinitrobenzene)sulfonamidophenyl-10,15,20-triphenyl porphyrin (TPP-DNB) was successfully constructed through the reaction formed thiol-sensitive sulfonamide bond between 2,4-dinitrobenzenesulfonyl chloride (DNBS) and 5-(4-aminophenyl)-10,15,20-triphenylporphyrin (TPP-NH₂). The structure of TPP-DNB was characterized by ¹H-NMR, ¹³C-NMR in CDCl₃ and elemental analysis. In addition, the compound had a melting point of 205℃. It was a brand new activable photosensitizer, whose fluorescence and singlet oxygen (¹O₂) of the photosensitizer were significantly quenched by 2,4-dinitrobenzene (DNB) motif and re-activated under the stimulation of dithiothreitol (DTT) or glutathione (GSH). The UV-visible absorption spectrum showed that TPP-DNB had a strong absorption peak at 425 nm (S band) and a weak but broad absorption band at 500-600 nm (Q band), which indicated that the compound had the similar absorption capacity as tetraphenylporphyrin (TPP) for UV light. The fluorescence intensity of TPP-DNB in PBS/DMF(99/1,volume ratio) at the wavelength of about 660 nm was very weak and significantly quenched by DNB primers compared to TPP's. The fluorescence intensity of TPP-DNB in the presence of DTT or GSH was gradually recovered with the increase of time and showed a tendency of strengthening, indicating that the fluorescence of TPP-DNB had a rapid stimulus response to thiols. The singlet oxygen yield of TPP-DNB was measured using DPBF as a capture reagent for ¹O₂. The results of ¹O₂ test showed that the singlet oxygen yield of TPP-DNB was 0.118 while elevated to 0.614 in the presence of DTT, which was close to that of the reference substance tetraphenylporphyrin (TPP) (0.62). These results indicated that singlet oxygen of the photosensitizer TPP-DNB was significantly inactivated and had thiol stimulated activation, which provided a new method for the design and development of activable photosensitizer.