Matching principal and interest method: loan principal: 320,000 yuan, assuming annual interest rate: 4.900%, loan term: 20 years, monthly repayment amount of principal and interest: 2094.22 yuan, total repayment amount of principal and interest: 502,665,438 yuan +02.8 yuan, * * interest payable:182,665,438 yuan +08 yuan. The interest paid in 1 month is:1306.67; The first 1 month principal repayment is: 787.55; Since then, the monthly interest repayment amount has decreased and the principal has increased. (without considering the adjustment of interest rate in the middle)