Admittance control is one of the distinct implementations for compliance control in robotics. In this paper, the admittance control for a cable-driven rehabilitation robot for upper-limb with three degrees of freedom (3-DOF) in three dimensional workspace is investigated. Admittance control is realized based on the interactive force between human and the end-effector, and human can fulfill desired trajectory without any reference trajectory by his or her active force which applied to the end-effector. The interactive force between human and the rehabilitation robot of admittance control is studied without disturbance as well as with a step response force disturbance, and the results are also compared to that of the traditional PID control under the same tracking performance. Results show that the admittance control algorithm has similar trajectory performance with PID control, and has lower interactive force in both situations. With active participation and low interactive force, the admittance control has great potential in rehabilitation robots.