Abstract: Aiming at the electromagnetic field in inhomogeneous medium,the establishing process of definite equations is investigated,combing with the first-order partial differential field equation and state relation,from the steady field to the time-varying field,the various forms of inhomogeneous partial differential equation with variable coefficients are given conceptually,which provids a theoretical basis for solving electromagnetic field problems.

Key words: inhomogeneous medium, electromagnetic field, partial differential equation