The method of changing the red code to the green code: the health code red code personnel need to complete the centralized isolation medical observation for 14 days, and do nucleic acid detection on the isolated 1, 4, 7 and 14 days respectively. If all the nucleic acid test results are negative, the isolation can be lifted and the health code can be changed to green code. However, if the nucleic acid test results are positive twice, COVID-19 will be diagnosed and then treated. After the treatment is completed, the isolation can be lifted and the health code can be restored to green code.