Abstract: In this paper,the instantaneous motions of a industrial robot at special configurations are analyzed,and the characteristics of the constrained motions,the direction of the permitted motion and the sub spaces of the existed rotational axes of the robot STANFORD at special configurations are discussed in detail.Furthermore,6 independent types at special configurations are obtained when the pitch of the reciprocal screw is zero.Finally,the general expressions of the reciprocal and existed motion screws in the reference coordinate system are given under all circumstances at special configurations and the atlas of the spatial motion is illustrated.