The annual interest rate of domestic major banks' loans is 4.35%, and the loan interest is equal to the total loan amount multiplied by the loan days multiplied by the daily interest rate, so the annual interest rate of 30,000 loans is 1.305 yuan. Loan refers to a kind of lending behavior that the lender provides monetary funds to the borrower on the condition that the principal and interest are repaid at the agreed interest rate and time limit according to certain loan principles. This kind of lending behavior consists of the object, condition, purpose, term, interest rate and method of lending. Interest refers to the monetary reward paid by the fund user to the fund owner in order to obtain the right to use the fund, and it is a form of expression of the time value of the fund. Interest is an ancient economic category, and the earliest form is usury interest.