Attention should be paid to opening credit cards: card issuers have certain autonomy in interest rate standards, interest-free repayment period and minimum repayment amount, liquidated damages, service fees, etc., which means that credit cards of different banks will be different in these aspects. Therefore, special attention should be paid when signing the application contract. The calculation method of credit card overdraft interest, whether to calculate and pay interest on credit card overpayment and its interest rate standard shall be determined by the card issuer independently. The interest rate will determine the calculation standard of the cardholder's interest when the repayment is overdue, so we should pay attention to whether the interest rate is reasonable and acceptable when signing the contract.