It's proposed reaction-diffusion mathematical model for evaluating efficiency and destruction area of brains' rumor under photodynamic-laser therapy. The modeling is based on physical mechanism of tissue's effect by singlet oxygen, which display oxidizer's function. Kinetic description of process is proceeded from model of M.J.C. van Gemert, that was worked out diffusion's mechanism of triplet oxygen's spreading in tissue under photodynamic therapy. All calculations are carried out for red laser with wavelength 630nm and photofrin2, as photosensitizer, and for the second type of photo-physical reactions of such molecules. The space-time tissue dependencies of concentrations of possibility conditions of oxygen and photosensitizers are calculated. As was theoretical shown, effect of photodynamic destruction of tumor by singlet oxygen, particularly in brain, not depends from intensity of laser's irradiation, but is dictated by summation does, which is absorbed by tissue in all time of process. The hyperhypoxic's effects in tumor, that accompany of photodynamic therapy, strongly increases with decreases of light's attenuation coefficient in tissue medium.