In this paper we study the scattering theory at low energy for nonlinear higher order wave equations.Our main tools are time-space estimates of linear higher-order wave equation.For this reason we first obtain the time-space estimates for linear higher-order wave equation by the technology of undertermined index and the method of functional Analysis which are different from the method of proof for classical wave equation,further we prove the estimates of nonlinear term in homogenous Sobolev space.Using time-space estimates and nonlinear estimates we obtain the scattering theory at low energy for nonlinear higher-order wave equation.Meanwhiles,we also obtain the global existence and uniqueness for nonlinear higher-order wave equations under condition of low energy.