Social surface defense and control: First, the maximum amount of police force sent to the front line, put into residential neighborhoods, vegetable farms, shopping malls, supermarkets, and other key areas, 24-hour patrols and guards, so that the masses to see the police are always on duty, safety is around. Secondly, police forces were organized to station at the site of nucleic acid screening, to do a good job of maintaining order, diverting the flow of people and preventing epidemics, etc., which cumulatively ensured that the nucleic acid screening of tens of millions of people was carried out smoothly. Third, more than 600 police officers were deployed in the city's Square Cabin Hospital to do a good job of on-site and off-site security management, police handling and public service. Tight community control: First, the public security police will work with all parties to form a grid-based inspection team to strengthen patrols in residential neighborhoods, and resolutely implement the requirements of "people do not move, do not leave the house". Second, the comprehensive use of video patrols, drones and police helicopters, such as high-altitude patrols, to strengthen the inspection and publicity tips, to return unauthorized persons out of the activity, and dissuade the crowd to gather and talk. Third, relying on "science and technology + manpower", the combination of big data analysis and grass-roots infrastructure work, public security police officers to give full play to the advantages of "familiar with the area, familiar with the head", and to increase the "sweeping the floor" "Street patrol" efforts to urge some "easy to miss" people to complete the nucleic acid test.