Abstract: By giving accurate inlet boundary condition of rotor to simulate the interaction between rotor and stator, the result of 3D unsteady numerical simulation to a row of rotor’s flow field can reflect the effect induced by upstream unsteady wakes. Because the number of rotor’s blades and stator’s blades is difference, traditional numerical simulation usually can’t accurately simulate the frequency of upstream unsteady excitation to downstream flow field. This difficulty can be solved by using this method. At the same time, the requirement of computational time and computational capability can be received. The result of numerical simulation to a low velocity axial flow compressor rotor shows that the aerodynamic performance of the rotor can be improved greatly if the deflected amplitude and frequency of upstream wakes were arranged reasonable. Therefore one kind of reasonable methods was presented to control and use unsteady flow in axial flow fan & compressor.