The forming and developing processes of high frequency acoustic combustion are studied with the method of computational modeling in this paper. The gas governing equations are described under the Euler coordinate，and the liquid phase governing equations are described under the Lagrangian coordinate. The high pressure combustion model is adopted. It is observed that the pressure oscillations near chamber head and convergence is greater than others when there is high frequency combustion instability in the chamber. After comparing the pressure，the temperature and velocity of the mixed gas under the condition of unstable combustion，the conclusion is drawn that the oscillation frequencies in two phase flow and combustor are the same when acoustic combustion occurs.