The model of flow around the flat plate cascades is a fundamental study for the flow-induced acoustic resonance phenomenon. Parker first conducted an experimental study on the acoustic issue with the vibration of the built-in plate in the rectangular pipe. It was found that the plate vibration amplitudes and the sound pressure level inside the pipe grow rapidly when the plate vortex frequency, the acoustic mode frequency and the natural frequency of the blade are the same, which is a new resonance mechanism. In this paper, a rectangular pipe built-in flat plate model is established on the basis of the Parker experimental model. A method combined the large eddy simulation used to process the flow field and the Lighthill acoustic analog used to capture the acoustic characteristics of the acoustic calculation model is proposed. The obtained sound pressure spectrum curves are highly consistent with the experimental data of Parker, which verifies the applicability and accuracy of the large eddy simulation and Lighthill acoustic analog calculation methods. The acoustic resonance problem of flat plate cascades is investigated using this method. The sound pressure spectrum curve at different flow velocities are obtained. The sudden jump of the sound pressure level when the acoustic resonance, the relationship between the characteristic frequency and the shedding vortex, and the anti-phase shedding mode of the shedding vortex at the trailing edge of the plate had been captured by taking the above methods for the flat plate cascades research. The flat plate cascades model established in this paper shows well the law of the plate shedding vortex motion and the sound pressure distribution characteristics under different incoming flow speeds. This paper may provides a model research method for the blade fracture problem caused by acoustic resonance of the aero-engine compressor.