Abstract: A high-order discontinuous Galerkin time-domain finite-element method based on Maxwell's curl equations is presented. It is a kind of domain decomposition method. Crank-Nicolson difference scheme is used for time-partial equation. Electric and magnetic fields are expanded using high-order vector basis functions with same order. Three-dimensional cavities are simulated to demonstrate accuracy and efficiency of the method. It shows that time step size is no longer restricted by Courant-Friedrich-Levy(CFL) condition.High-order vector basis function could improve accuracy compared with Whitney 1-form vector basis function.