To investigate the effects of photodynamic diagnose(PDD)and photodyn amic therapy(PDT)of colon cancer by using the new phthalocyanine photosensitizer T1,the fluorescence and a bsorption spectra (200－800nm) of photosensitizer T1were detected in vitro.The MTT assay was performed to meas ure the effects of T1-mediated PDT on both colon cancer cells (CT-26,LoVo) and normal cells (fibroblasts L929).Animal models were established using 30male BALB/c nude mice,which were randomi zed into control group,tumor group and PDD group with 10mice in each group.Fluorescence spectrophotometer w as employed to detect the spectrum.The results show that the maximum absorption peak of T1is located in the near-infrared region,which meets the characteristics of phthalocyanines.There is no significant change in f ibroblasts proliferation treated by T1-PDT in presence of light,but for colon cancer cells,the prolife ration is inhibited.The spectrogram suggests that the spectral curve of the control group is smoother and the abso rption intensity is much weaker than that of the tumor group.Since the spectral curves between the tumor group a nd the PDD group are parallel,the peak-to-peak values of the two groups are slightly different.The absorption intensity of the tumor group is lower compared with that of the PDD group.T1photosensitizer has obvious influen ce on the PDD and PDT for the colon cancer,which would provide a fresh combination strategy for the diagnosis and t herapy of colon cancer during the early stage.