Abstract: In the multi-level hybrid feed support system of the Five-hundred-meter Aperture Spherical radio Telescope (FAST),the cabin's time-varying barycenter can cause the terminal feed receiver's pose error.In order to ensure the tracking accuracy of astronomical observations,firstly the elastic mechanics model of the cable-driven parallel mechanism is deduced, and the relationship between the cabin's barycenter location and the feed receiver's pose error is illustrated.Then the change law of the cabin's barycenter is studied.Finally,the Newton-Raphson method is adopted to iteratively get the range of the feed receiver's pose error caused by the time-varying barycenter.The maximum position and orientation errors are respectively 120mm and 1.40°,which can't meet the astronomical observations' accuracy requirement.So the cabin-barycenter change should be considered in the prototype design,vibration control and precision control.