Hemorrhagic shock is clinically classified into four grades: grade I is the loss of human blood volume about 750 ml, the clinical will appear tachycardia, blood pressure and respiration will not change much. Grade II is the loss of human blood volume about 1000-1250ml, in this case the patient will appear tachycardia, systolic blood pressure may be reduced, pulse pressure difference will also be reduced. Grade III is more severe bleeding, where the patient loses blood volume rapidly for a short period of time about 1500-2000 ml. Grade IV is fatal blood loss, the blood loss can reach about 2000-3000ml, if not resuscitated in time, cardiac arrest will occur immediately, so grade IV should be rapidly transfused, and some need emergency surgery.