The space motion control problem of a 2-DOF cable-driven parallel mechanism is studied based on PD control and feed-forward control method. Firstly, the space motion mathematical model of the system is formulated based on the Lagrange's equation. In order to ensure that all the cables have always remained in tension in the workspace of the mechanism, the cable internal force principle is applied to the proposed control method. Then, based on the Lyapunov stability theory, the stability of the closed-loop system is proved. Finally, to test the correctness of the proposed control strategy, simulation and experiment results are given. Approximate consistency between simulation and experimental results proves the validity and the rationality of the proposed control strategy.