First of all, the red health code may be due to a certain scale of epidemic in the area where the parties are located, such as more than 50 confirmed cases or cluster epidemics, which will lead to a high risk level in this area. At this point, the health code will turn red for people who have stayed in the area or stayed in the area. Secondly, when the health code turns red, the number attribution should be considered abnormal. The use of smart phones has become very common, and everyone has their own number. During use, the device will send a signal remotely to record the trip. If the currently used calling card has abnormal attribution and is located in other medium and high risk areas, the health code may turn red even if it does not go out. In addition, different users of primary and secondary cards and abnormal signals of communication company base stations may also lead to similar situations.