1. Key monitoring of bank risk control system: every bank has a risk control system to monitor the use of users' credit cards at all times. Once the customer's credit card usage is abnormal, such as large cash withdrawal or abnormal operation, it will immediately trigger the bank risk control mechanism. At this time, the bank's system will focus on monitoring the customer's credit card, perhaps by reducing the limit first and then observing for a period of time, or by directly sealing the card. 2. Repeated overdue repayment of credit cards: Some banks will not reduce the quota, let alone seal the card, even if the customer is overdue once. However, in the case of many overdue customers, banks have reduced the credit card quota of such customers. If the overdue repayment is not good, the bank will also directly seal the card. 3. The credit card limit is too small: Some friends will not use it for a long time after applying for a credit card, or the amount used is less than 30% or even 20% of the credit card limit. Then the bank will judge your consumption potential at this time, and it is likely to reduce your credit card. 4. Brush a large amount: When your credit card has a large amount, such as one or two thousand, if you brush all the credit cards at once, then such an operation can easily trigger the bank's risk control system. Once monitored by the bank's risk control system, credit cards are likely to be downgraded.