The indications for blood transfusion mainly include massive blood loss, anemia, hypoalbuminemia, etc., and its principles include hemoglobin <70g/L can be imported to concentrate red blood cells, etc.. The indications for blood transfusion include massive blood loss to replenish blood volume, anemia or hypoalbuminemia, blood transfusion to correct anemia, replenish plasma or albumin, etc.; severe infections, input of concentrated granulocytes can help control the infection; coagulation abnormality, fresh frozen plasma is often input to prevent and treat bleeding caused by this, and so on. Transfusion guidelines suggest that hemoglobin >100g/L does not require transfusion; hemoglobin <70g/L can be entered into the red blood cell concentrate; hemoglobin between the two, should be based on the patient's specific circumstances to decide whether to transfuse. When the platelet count is <100x10^9/L, the decision of whether to transfuse platelets should be based on whether there is spontaneous bleeding, part of the wound oozing blood, and so on. It should be noted that the need for blood transfusion should be decided under the guidance of a doctor according to the patient's condition.