The data curve of step-drawdown test on the logarithmic scale shows a characteristic form according to the aquifer concerned. The curve bends generally at a certain point and is divided into two segments of different gradient. The point is called by the term of transition point and the form of curve of transition form respectively. The transition form may be due to the hydrogeological characters of aquifer and its confining beds. The writer classified the type of form and considered the cause of transition and the meaning of form on a few assumptions.