After HIV exposure occurs, if it is a traumatic operation such as a needle stick injury, the wound should be squeezed out promptly to squeeze out the blood. The wound should be rinsed under running water as soon as possible, and should be thoroughly cleaned and disinfected with alcohol. After that, you should take the HIV blocking medication as soon as possible within 2 hours for a period of 28 days. If it is not possible to take it within 2 hours, it should be taken within 48 hours to still achieve the blocking effect. If you are unable to take it within 2 hours, you should take it within 48 hours to achieve the blocking effect. If you take it after 48 hours, you should take it within 72 hours to achieve the blocking effect. After the blockade is completed, a test should be performed at 3 months and 6 months to determine if the blockade is successful.