This paper describes the power assistive algorithm and effectiveness of an end-effector typed walking rehabilitation robot capable of power assistance of lower extremity. The proposed walking rehabilitation robot has three walking modes; the first is the continuous passive mode (CPM) that power assistance is constantly provided, the second is the continuous active mode (CAM) that the patient has to walk without power assistance, and the third is the assisted passive mode (APM) which assists the patient during walking by recognizing the walking intention. The working principles of these three walking rehabilitation modes are proposed and the power assistive performances of the three modes were verified through EMG measurement tests.