The use of tourniquet is relatively simple, you need to wrap the tourniquet to the bleeding site above or and proximal to the end. The precaution is to pay attention to its tightness to avoid necrosis of the limb. 1. Usage: the use of tourniquet is relatively simple, but the principle is more complex, only master these principles can play a life-saving role. Before putting on the tourniquet, the injured limb should be elevated to promote the venous blood flow back into the body and reduce blood loss. And under the premise of effective hemostasis as close as possible to the bleeding part, when tying the tourniquet its tightness to just press the arterial bleeding as appropriate. 2. Precautions: for the use of tourniquet for the injured, there should be a clear sign, need to be written near the tourniquet or the skin on the use of tourniquet time, to prevent ischemic necrosis of the limb. And the tourniquet needs to be relaxed for 1-2 minutes every 40-60 minutes. The total time of stopping bleeding with tourniquet should not exceed 4 hours in general, otherwise the limb is prone to necrosis. It should be noted that this method of hemostasis is forbidden when there is obvious ischemia in the distal part of the injured limb or when there is serious compression injury. And at the same time, stop bleeding, should be close to the nearest medical care.