For a several decades, myoelectric control of robotic prosthesis has used electromyograpy (EMG) as its control input to infer human intention. In this paper, we propose to use impedance change of musculoskeletal system to estimate kinematics change of human hand in prosthesis control based on its several features superior to the EMG as follows: clearer signal with much less noise so is less delay caused by filtering and little change of the signal at stationary state of hand motion. We investigated these features of electrical impedance myography (EIM) through several experiments. The result shows it is only minute change of signal occurs at the stationary pose. Although it is sensitive to the motion of other parts (e.g. elbow), it is surely a promising signal for the control of robotic prosthetic hand.