Abstract: Photosensitization technique is a newly developed method to detect and treat tumo- rs.The study has been carried out in this hospital since 1981 and a preliminary summ- erization is following: The absorptive and fluorescent spectrums of Chinese HPD,measured with fluoresc- ence spectrophotometer,comparing with USA HPD.The spectrums are same in princi- ple.We found that the absorption ratio of tumor to muscle is 12.52-14.47 within 48- 72 hours after injection of HPD to mice implanted with S₁₈₀. Observing tumor cell fluorescence and killing effect on single layer cell culture,we also find that HPD enters into the protoplasm of tumor cells and shows homogeneous red fluorescence.That tumor cells （PLA 801,PLA 802） were killed under the PRT. For shallow and surface lesions containing HPD,we can get a clear red fluoresecence when using ultraviolet light as exitation source for treatment,broad band incoherent light can be used.On the basis of basic research the effect of PRT and mechanisms of photosensitization are reported.It appears that PRT provides a new promissing me- thod for early diagnosis and treatment of malignant tumors.