Abstract: A united hyperbolic function method to find the solitary wave solutions to nonlinear evolution equations was proposed‚and two kinds of solitary wave solutions to the combined KdV-mKdV equation were obtained by this method．As a special example‚two kinds of solitary wave solutions to the mKdV equation can be obtained‚and the bel- lshaped solution to the KdV equation was also given．The proposed method is based on the fact that the solitary wave solutions are essentially of a localized nature．In this method‚the solitary wave solutions to a nonlinear wave equation are denoted as the polynomials of hyperbolic functions‚and the nonlinear wave equation is changed into nonlinear alge-braic equations．So the hyperbolic function method is simple and effective when used to study the solitary wave solu-tions of the nonlinear evolution equation．

Key words: nonlinear evolution equation, solitary wave solution, hyperbolic function method, combined KdV-mKdV equation