Analysis of Salt Wedge in the estuary is very important in Japan now. It is very dificult, however, to carry out theoretical analysis by the fundamental differential equation of motion of salt wedge. Poggi's or Morgan and Farmer's solution are nothing more than a practical equations. At present, fortunately, digitial computers are common in Institutes and Uneversities in Japan. The characteristics of salt wedge in estuary was studied by, the computer KDC-1 of Kyoto University. By this numerical analysis, several characteristics of salt wedge were known as are presented in this paper.