Raman tweezers is used to probe the oxygen carrying capacity of erythrocytes.The effects of laser power on erythrocytes are compared.An indicator for distinguishing oxygenated and deoxygenated erythrocytes is chosen and utilized to analyze the oxygen carrying capacity of erythrocytes from different storage time and different health state.The result shows that strong power of laser led to the bands at 1 248,1 371 cm－1,the markers of heme aggregation,increasing.The ratio I1 638/I1 547, a well indicator for distinguishing oxygenated state from deoxygenated state,reveals that the oxygen binding capacity of preserved erythrocytes increase as storage time extending,while the deoxidization capacity is not change significantly.Erythrocytes from HbH-CS,an alpha-thalassemia disease,are easier to oxygenate than normal controls,but difficult to deoxygenate.The findings demonstrate Raman tweezers can be a rapid,non-invasive,sensitive technique for analyzing and evaluating the oxygen carrying capacity of erythrocytes.