In order to rapidly estimate the far-field sound pressure level of discrete noise in an axial-flow compressor, the unsteady internal flow field of a single-stage compressor with an outlet guide vane was numerically studied by computational fluid dynamics (CFD) method. The position and mechanism of discrete monotone generation were analyzed according to the results of the flow field. On this basis, the computational aeroacoustics (CAA) method combined with finite element / infinite element technique is used to simulate the compressor noise under two operating conditions, and the radiation characteristics of near-field / far-field compressor discrete noise are analyzed. The numerical simulation results show that the calculated results of the hybrid method are in good agreement with the experimental data, and can be used for the rapid evaluation of compressor discrete noise.