The injection site of LMWH is usually subcutaneous injection or intravenous administration. In the choice of subcutaneous injection, the abdomen is the best injection location, because the abdomen injection area is large, subcutaneous fat, relatively few capillaries, subcutaneous temperature is constant, drug absorption is fast, not affected by exercise. At the time of injection, 5cm above or 5cm below the umbilicus was selected as the upper and lower boundary, and 5cm inside and outside the midline of the clavicle was selected as the left and right sides. Avoiding the midline of the umbilicus, injections were given twice alternately at left and right sides, with the interval between injection points being 2cm. Massage the local skin for 2 minutes before the injection until the skin is red, lie flat, bend the knees and sit down, disinfect the local skin, and ask the patient to lift the skin on the abdominal wall to form folds and vertical angles, pull out the needle cap for injection.