Abstract: A new kind of measuring instrument is studied which is applied to research thestatic and motional reactions of the foot sole of a walking mechanism.Its measuringprinciple and construction as well as error-analysis method are introduced.Taking awalking robot with bilegs for example,the authors actually have measured the groundreaction and its variation during its normal walking.On the basis of this,some ana-lyses have been made and finally proper conclusions are drawn.The results are ofparticular value to gain planning,motion planning and ZMP planning.With our usingthis instrument,the walking path during ZMP walking is measured with success.