To find the reason of limiting hole fracture and over-expected vibration amplitude on the mechanical environmental test to a Close Cable Loop(CCL) under only single-axial inner-plane swept frequency excitation, the finite segment method of multi-body dynamics was introduced to model and simulate the cable system with a concentrated mass and a position limiting hole, the cable vibration response and the contact force in limiting hole were obtained. The results showed that the vibration response started from inner-plane vibration to outer-plane vibration and to continuous rotational vibration. Cable vibration amplitude enhanced continuously due to rotational vibration process, and attenuated suddenly. The response process and vibration amplitude was coincided with the test. Continuous rotational vibration under swept frequency excitation is the key reason for the problem of fractures.