The equal principal and interest repayment method in mortgage repayment is a variable installment payment, which is wrong. According to relevant public information inquiries, equal principal and interest is a type of installment payment. Equal principal and interest refers to the repayment method of a home purchase loan, which is to repay the same amount of the loan (including principal and interest) every month during the repayment period. The equal principal and interest repayment method in mortgage repayment is repayment in equal installments.