Abstract: Numerical simulation of self-excited thermoacoustic oscillation in a Rijke tube was performed in order to research the mechanism of the excitation and controlling strategy of thermoacoustic instabilities. Acoustic perturbation equations with nonlinear heat source were solved by computational aeroaeoustics, which was less dispersive and dissipa- tive. The influence of different heat sources and boundary conditions to nonlinear effects was researched. The results showed that, the start- oscillation phenomenon and the limited cycle can be obtained by computational aeroacousties. The nonlinear behavior commenced at 1/3 of the mean flow velocity. Compared to the heat source, the influence of the nonlinear boundary was small, especially on the amplitude and spectrum. The numerical results showed good consis- tency with experiment. It turns out that, computational aeroaeoustics is available to the simulation of thermoacoustic oscillation.