It is the perpose of this paper to devide fundamental data for analysis of flow on over-flow spillway. There are still ploblems on assumption that the stream-line are coaxial circle, which has been used on analysis. We attempt to obtain a new interpretation on character of stream-line with Hele Shaw model. because it is impossible to express the stream-line analytically. We report the results of measurement on stream-line and compared water surface profile with Hele Shaw model and two dimentional experiments after Araki and Fujimoto. It became clear that deviation of stream-line from coaxial circle is fairly large, and it is neccesary to introduce on analysis of flow on over-flow spillway.