Abstract: This paper describes a rigid body motion with a fixed point by rotated tensor and avoids the meted problem that when one describes a rigid body motion with a fixed point by angular displacement,namely,the attribute of it is different for finite and infinitesimal sizes.We also verify that both the angular displacement vector and rotated tensor can describe respectively the motion of an infinitesimal rigid body rotation with a fixed point.Both are equivalent.

Key words: rotation around a fixed point, tensor, vecto