Taking the mortgage interest rate,short-term interest and house price as three risk sources,and considering not only the prepayment risk induced by decline of mortgage rate and rise of house price,but also the default risk induced by decline of house price,this paper extended the paper of Kariya et al in 2000,and developed a 3-factor pricing model for fixed rate mortgage-backed securities.

Based on prepayment intensity process,the valuation of fixed-rate mortgage contracts is studied and an equilibrium model is built with the specification of a game between the representative mortgagor and the market whose optimal strategy are about the endogenous mortgage rates and whether to refinance a new contract or continue with the current one,respectively.