A lean rotor is designed on the basis of NASA rotor 11 original blade. The performances of above two rotors are obtained by the steady computation, and the results show that the lean rotor can improve the rotor performance, especially the stall margin. To investigate the rotor interaction to the upstream stator, this paper simulates the unsteady flow fields of stator-lean rotor and stator-original rotor, and the numerical results indicate that compared to the original rotor the lean rotor interaction to upstream stator blade is weaker in one period. The one-period tip region flow comparisons of original rotor and lean rotor show that the flow can more easily pass through the lean rotor tip region than the original rotor 11.