This paper focuses on the capacity changes of the red blood cells carrying and releasing oxygen. In order to provide theoretical basis and guidance for the clinical treatment of uncontrolled hemorrhagic shock, we investigated cases in the occurrence of uncontrolled hemorrhagic shock, and also analyzed the mechanism of physiological cause. Twenty healthy SD rats were used to build the hemorrhagic shock model. Red blood cells were collected at the initial step, at blood lose 20%, 30%, and 40% to determine the red blood cells capacities of carrying and releasing oxygen. The Hemox-analyzer was used to measure the thermodynamic parameters of the P50, the kinetic parameters of Tc50 and Tr50. The 2,3-DPG, pH value, glucose and lactate dehydrogenase changes were also captured and recorded. With the aggravation of shock, P50 and lactate dehydrogenase are continuously increased, Tr50, pH value and glucose are tended to reduce significantly, and Tc50 does not change significantly. With the increase of blood loss, red blood cell capacity to carry oxygen is stable, and the ability to release oxygen is increased, so that the oxygen consumption cannot be satisfied, which causes organ failure.