In this paper, the spectral element method is used to build a hydrodynamic model in order to solve the semiconductor transient simulation. The hydrodynamic model consists of five nonlinear differential equations: the electron current continuity equation and hole current continuity equation, electron energy-balance equation, hole energy-balance equation and Poisson's equation. Unlike the drift-diffusion(DD) model, the hydrodynamic model can simulate the deep sub-micrometer device to get more accuracy results than the DD model.