The accumulation of photo-sensitizer Talaporfin (another name is NPe6) in cancer cells after incubating in NPe6 solution has been investigated. It was confirmed that Talaporfin can only kill cancer cells selectively by photo-irradiation at certain wavelengths. In this experiment, the WFB (rat fetus fibroblast) and W31 (the malignant transformed cell from WFB) were used as normal and cancer cell. The measurement of the optical absorbance of Talaporfin within the cell confirmed that the Talaporfin was accumulated in cancer cells more than in normal cells. Fluorescence image of cancer cell after incubating in Talaporfin solution was measured with a fluorescence microspectrometer. For comparison the standard white light image of cancer cell was also taken. A semiconductor laser was used as PDT (photodynamic therapy) optical source to compare the photocytotoxicity effect of the W31 and WFB cell. The viability of the cells was assessed by use Trypan Blue Stain. It was clarified that Talaporfin could be accumulated in cancer cells more than in normal cells and lead to cancer cell death selectively after irradiation.