3403. 17 yuan. The matching principal and interest repayment method stipulates that the monthly payment of 300,000 loans for 20 years is 3,403.17 yuan, and the average capital repayment method stipulates that the monthly payment of 300,000 loans for 20 years is 465,438+025 yuan, and then decreases month by month. Calculation formula of monthly mortgage payment: [monthly mortgage payment = [loan principal × monthly interest rate ×( 1 interest rate )× repayment months ]=[( 1 interest rate )× repayment months].