The purpose of this study was to develop a rational and practical test for estimating the co-ordination ability of strength exertion (CASE) and to examine scale and description forms, test time and estimation time. A total of 89 college students were used as subjects. The test method was form fitting the exertion value of grip strength (GS) to the demand value appeared on display of personal computer (PC). A test of CASE was performed using 3 kinds of description forms on display of PC : bar chart, number, and wave. The demand values of bar chart and the other two were sinusoidal wave form of 0.3 Hz and 0.1 Hz, respectively. Tracking wave was the range from 5% to 25% of maximal grip strength value. The variables estimating CASE were measured by PC both 1) a maximal lag (ML1) and 2) the sum total of lag (SL2), between the demand and GS value (see Figure 5). The findings in this study can be summarized as follows : 1) It is a valid method to estimate by the rest time except the first 5-second period from the beginning of test because its mean value showed significantly larger than those in every other 5-second period both ML1 and SL2. 2) In estimating CASE, the scale form of kg unit is more effective than that of %. 3) Both tests of number and wave description form, the reliability of SL2 in the test for 30 seconds showed significantly higher value than that in the test for 60 seconds. Therefore it seemed that the test for 30 seconds is more effective. 4) The test of number description form was difficult for subjects to pursuit the demand value.Judged from the result of reliability, it seemed that bar chart and wave description forms are effective tests.