A robot system is present for the wind turbine blade grinding work. The robot is a mobile manipulator equipped with a grinding tool. In order to realize the compliant control of the operation force, a robust impedance controller is present in the presence of coupling factors between the mobile platform and manipulator, modeling uncertainties and existing bounded disturbances. The proposed control strategies guarantee that the system motion converges to the desired manifold and the desired constraint force. Simulation experiment has been done and the experiment results show that, the presented control method can realize the robust control of mobile manipulator, and thus show the effectiveness and correctness of the designed controller.