Studying the denaturation of oxidative hemoglobin of blood preserved at room temperature, it is helpful to overall understand erythrocyte injurious during blood preserved at room temperature. Using electron spin resonance technique, we have researched the denaturation of oxidative hemoglobin of blood preserved at 35 degrees C. We discovered that blood preserved at 35 degrees C, appears ESR absorption of high spin methemoglobin (g = 6) after preservation time is 36 hours. The high spin methemoglobin ESF absorption will increase when preservation time increases. When blood is preserved at 4 degrees C, it dose not emerge ESR absorption during 60 hours preservation. SOD activity will gradually decline in erythrocyte of blood preserved at 35 degrees C when preservation time increases. Oxidative denaturation of hemoglobin is probably caused with gradual declining of antioxidation system effect in erythrocyte.