On the basis of the international evaluation of impairment of hand function, we propose five improvements: (1) For the evaluation of the impairment of thumb opposition and adduction, calculating the ratio of two distances takes the place of measuring a pure distance. (2) Hand sensory impairment evaluation is based upon both results of a sensory examination and a two-point discrimination test. (3) On the evaluation of amputation percentages related to whole hand, measuring loss of length is replaced by measuring loss of area. (4) On the evaluation of a joint, we correlated the combined angular measurement with the loss of length. (5) In the international evaluation of impairment of hand function, the sensory or amputation of the palm and back of the hand is not counted. But they are counted in our paper. Besides above-mentioned works, we have made a software with these improvements. You may obtain definite impairment percentages related to whole hand, so long as you input the results of examination of hand function.