The purpose of this study was 1) to estimate a ratio scale index predicting the wins of judoist, and 2) to Predict the probability of wins in the All Japan Judo Championship Competition '81 with the results of some tournament games competed beforehand. One hundred and eighty excellent judoists who participated in the All Japan Judo Championship Competition and others from '75 to '80 were selected as the Subjects. And then, Bradley-Terry model was applied so as to prepare a prediction-formulus for the All Japan Judo Champion-ship Competition '81. A basic assumption that one dimensional scaling was constructed with following formula ; P_ =P_P_/ (P_P_+P_P_), where P_ stands for probability that i-th judoist with j-th, maximum likelihood method was applied to estimate a ratio scale index of judoist. And then, the probability of wins in the All Japan Judo Championship '81 was predicted by the computer simulation. Testing the validity of this ratio scale and prediction showed that this Bradley-Terry model was very efficient in its practical use.