This paper presents result of application of spectral element method (SEM) for simulation of wave propagation in a beam structure and the crack is simulated by node separation method. Wave propagation characteristics in an aluminum beam structure are investigated. And the simulated results are compared with the analytical result from Lamb equation to validate the proposed model. The influence of cracks with different damage degrees to response signal are investigated and the damage detection method are studied. The conclusion can be useful for study of damage detection method based on Lamb wave.