For random sonic fatigue problem of thin-walled structures, this paper put the calculation formula for mean-amplitude conditional probability of rain flow loop based on the vibrational response power spectral density(PSD) of structures subjected to acoustic loadings, combined with Dirlik experience formula for the amplitude probability density of a rain flow loop, the practical algorithm is derived for calculating the joint mean-amplitude probability density of rain flow loop, which effectively overcome the limitation caused by that only the amplitude can be considered for fatigue life estimation, and the mean values of rain flow loop are ignored. According to Miner linear cumulative damage theory, the estimation method for sonic fatigue life is build up by applying the obtained joint probability density. As an numerical example, an aeroengine combustor liner structure is selected, the vibrational response is simulated by using coupled finite element method (FEM) and boundary element method (BEM), and based on the results of stress response, the sonic fatigue life of the liner is estimated by applying the proposed method. The influences of different sound pressure levels on fatigue life of the liner are emphatically analyzed. The results show that the method proposed in this paper is of adaptability for sonic fatigue life analys is of aero-thin-walled structures.