The relationship between polhode and herpolhode of the instant center of a rigid body when it makes a plane paraller motion is presented.

给体在平面平行运动时，体瞬心的本体极迹极迹关系的一证明方法.

A certification method to the relationship between polhode cone and herpolhode cone is given when the rigid body is in a fixed point motion.

摘要给体定点运动时本体极面极面关系的一证明方法。