The new exact solutions to Klein-Gordon equation under a general function transform

A modified double Jacobian elliptic function expansion method under a general function transform,which is more general than the Jacobian elliptic function expansion method under a traveling wave transform,is proposed to construct the exact periodic solutions of nonlinear evolution equation. It is shown that some new exact periodic solutions of nonlinear Klein-Gordon equation are obtained by using this method and the known results of the Klein-Gordon equation are replenished.When the modulus m→1 or m→0,these solutions degenerate into homologous separate wave solution,trigonometric function solution and strange traveling wave solution.