The specific clinical steps for blood sampling are as follows: 1. Inform the patient of the purpose of the blood sampling and the precautions to be taken to reduce the patient’s anxiety and fear. 2. Ligate a tourniquet on the arm to be bled and ask the patient to make a fist to fill the blood vessel. 3. Find a vessel with good elasticity and disinfect it 2-3 times. 4. Enter the needle obliquely at an angle of 30 degrees to the vessel, enter the vessel and then parallel the vessel for 1-2 cm. The end of the puncture needle is immediately connected to the blood sampling test tube. 5. After sufficient blood is retained for laboratory testing, the puncture needle is quickly withdrawn and the swab is locally pressurized at the puncture site. The patient is instructed to apply pressure for 3-5 minutes, avoiding local kneading to avoid the formation of hematoma, then the blood draw is completed.