Abstract: The dynamic singularity of the flexible manipulators is studied. Firstly, the reason that cause the dynamic singularity of the flexible manipulators is analyzed. The factors which influence the dynamic singularity is confirmed. The factors include the direction of the outside force, the strength of the outside force, the value of the damp, the relative between the frequency of a outside force and the natural frequency of a flexible manipulator during they are in resonance sidebands and the value of the natural frequency of the flexible manipulator. Then the criterion of the dynamic singularity and the method to avoiding the dynamic singularity are proposed. Finally, a space manipulator with three arms (the last arm is flexible) is simulated，and the theoretical analysis is verified to be correct.

Key words: Dynamic singularity, Flexible manipulator, Natural frequency, Resonance, 2 rotations and 1 translation, continuous rotation, continuous rotation axis, parallel mechanism