We studied the effect of flexor tendon force ratio with regard to the grip force and the finger joint angle on power grip motion in a cadaver model using the hand motion simulator. The hand motion simulator was developed with a force delivery unit and data acquisition system. The simulator controlled both flexor tendon forces (FDP and FDS) ranged from 1:1 to 1:6 of FD:FDP. 40% of FDS force to total tendon force (i.e. 3:2 FDP to FDS) showed the highest grip force. Also, the internal tendon force was 5.3 times higher than externally applied grip force, and the efficiency of the forces was best at the 3:2 FDP to FDS force ratio. The finger joint angles were changed according to the tendon force ratios of FDP to FDS. These results demonstrate that awkward finger motion and posture may lose the force efficiency between internal and external forces and cause higher internal impact that may be a risk factor causing carpal tunnel syndrome.