The research based on the theory of porous medium heat and mass transfer，combined with the mechanism and characteristics of heat mass transfer in radio-frequency and convective drying，establish the mathematical model and give the definite condition through mass momentum and energy conservation equations. Each independent and dependent variable has independent control equation. Use the finite volume method to establish difference equation for to decouple the coupled partial differential equations，so that each independent variable can be solved independently when programming in Matlab or FORTRAN .