The reason why the repayment principal of student loan 20 17 is more than 20 16 is that the repayment method of student loan is equal principal and interest method. Equal principal and interest method: the monthly repayment amount is equal, the interest expenditure in the early stage is large, and the proportion of principal in the later stage is large. The interest ratio is large, and the principal ratio is large after half of the repayment period.