To reveal hemolysis phenomena induced by a photosensitization reaction with its environment, we measured absorption spectrum of a blood sample to analyze hemoglobin oxidation and resolved oxygen desorption dynamics. The quartz glass cell with 1 mm optical path length was used as a cuvette. Red blood cell suspension medium of 0.625 hematocrit with 30 μg/ml talaporfin sodium was used as a sample. A red diode laser of 664 nm wavelength was emitted to the cuvette with 120 mW/cm2 in irradiance for 40 J/cm2. Absorption spectra of the sample were obtained before and after the photosensitization reaction by a spectrophotometer. Multiple regression analysis was employed to obtain concentrations of various hemoglobin species from measured absorption spectrum. Comparing to 0 and 40 J/cm2, methemoglobin and deoxygenated hemoglobin concentrations increased 0.19 g/dL and 0.02 g/dL, respectively. Oxygenated hemoglobin concentration decreased 0.17 g/dL. Oxygen environment could also be presented by oxygen pressure calculated from the concentrations of oxygenated hemoglobin and deoxygenated hemoglobin. These obtained hemoglobin concentration changes might indicate hemolysis progress and oxygen environment. We think this simple optical measurement could reveal both the hemolysis and oxygen environment.