Abstract: A linear stability model of rotating stall in axial flow fan/compressors was presented based on direct numerical methods to Navier-Stokes equations,which was described as an eigenvalue problem.The inception point of rotating stall can be predicted by the model without requiring more experimental or empirical relations as input data.Two different methods,finite difference method and spectral collocation method,have been proposed to discretize the eigenvalue equation and the relevant comparison and analysis also have been given in the present investigation.