Abstract: A noise suppression method for deformable open cavity based on a drain channel is proposed: a series drain channel is designed on the back wall of the cavity, and the inclination angle of the bottom plate and the back wall of the cavity can be changed with the change of flow rate through the actuator, so as to achieve the best effect of cavity noise suppression under different flow rates. The large eddy simulation combined with computational aeroacoustics is used to simulate a typical open cavity. It is found that the overall sound pressure level and the main modal sound pressure level of the cavity noise would both decrease as the inclination angle of the back wall θ changed, and the decrease amplitude would increase as θ increased, showing a positive correlation. Furthermore, the modal frequency of the cavity noise would shift significantly to lower frequencies. The results show that the noise suppression method for deformable cavity based on drain channel can significantly reduce the overall sound pressure level and the main modal sound pressure level of cavity noise, and at the same time, make the main modal frequency move significantly, which can effectively avoid the cavity structure and the equipment in the cavity vibration and acoustic fatigue damage.