Before performing venous blood collection, it is important to choose a suitable vein for puncture, try to ensure a successful one-time puncture, and perform strict disinfection near the puncture site, paying attention to the whole process of aseptic operation to avoid causing infection. If the patient has good vascular elasticity and it is easy to puncture, the angle of puncture can be elevated as much as possible to reduce the patient’s pain. If the vascular condition of the elderly is poor and difficult to puncture, the angle of the puncture needle can be lowered to increase the success rate of the puncture, and care should be taken to avoid puncturing the blood vessels to avoid subcutaneous bleeding and bruising. When collecting blood, it is important to collect enough blood for testing according to the blood collection tubes used and the test items performed, and to avoid coagulation and hemolysis of blood in the blood collection tubes.