In this paper, kinematics redundancy of a flexible redundant manipulator (FRM) is employed to alleviate the impact vibration resulting from objects grasping. A vibration-alleviating measure (VAM) of the FRM, and a vibration-alleviating ellipsoid (VAE) with respect to the measure are defined. A method to determine the pre-posed configuration of an FRM is presented based on the defined VAM and VAE. A finite-element model is used to describe the FRM's dynamics incorporating the grasped object. Simulation conducted on a planar FRM shows that the FRM experiences relatively less impact vibration at the pre-posed configuration determined by using the presented method.