high frequency instability in liquid rocket engine is simulated by the method of computational fluid dynamics. The gas controlling equations are described under the Euler coordinate. The liquid phase controlling equations are described under the Lagrangian coordinate. The turbulence model is κ-ε model of high Reynolds number. To assess the combustion instability, the sinusoidal pulse is put into the combustor. The calculated results are observed by the way of Rayleigh mechanism of sound amplification by heat release. The curve of combustion stability is plotted to various perturbation and initial droplet diameter.