"The "Ecological Geometry" has a possibility to substitute the Euclidean geometry for architectural design. This theory treats the visual flow in a view that appears when we walk in city space. That is, it has a possibility to explain the architectural environment directly that we are experimenting. The Ecological Geometry is the system of the coordinates contained our view directly. It is possible to expresses the peculiar of our visual experiences in each place. Compared with the Euclidean Geometry that based on x-y-z coordinates separated from our view. Some designers and researchers mentioned about experiences of our walking sequence. But it seems that many of them tend to be explained by visual experience like a slide show. We try to observe differential changes in the view appeared by walking. When one walks in the city space and even when he/she stays there, he/she usually catches the buildings as swaying the body and changing the view subtly and unconsciously. When one walks through the city space, the backward buildings may appear in the view from behind the front buildings gradually; or when one walks under an elevated railroad, it will expand gradually in the upper part of the view. The combination of these differential changes makes the characteristic of visual experience on each place of the city. These changes correspond with the arrangement of buildings. In this study, we aimed to explain the quality obtained from our experience in each place and tried to make clear the relation between an optical flow and the composition of city buildings. Three areas were researched :(Chayamachi-area, Sonezaki-area and the area in front of Osaka station) with different scale, differ buildings form, and different density of the arrangement. We were filmed a walking scene randomly. Visual experiences from the viewpoint of relation between an optical flow and the composition of city buildings were classified :(1) dive (2) walk through (3) covered (4) jump out (5) spread out (6) edge up. When comparing the three areas, it seems that the arrangement of the buildings and the pattern of our walk were somewhat related to each other. The former can be classified in more detail into density (low and high), the proportion of arrangement (straight, latticed, random etc.), uniformity of the size, volume of the buildings (tower, band, cube, a curved surface, a place surface etc.), and the latter into (1) walk toward the building (2) walk along the building. In Chayamachi area where small buildings stand closely together, the optical flow in the view changes dynamically with a little move. In front of Osaka station, where large buildings stand separately, the flow changes gradually. It is different from the combination of the vertical elements (e.g. high-rise buildings) and horizontal elements (e.g. elevated railroad) by arrangement of the building.Now, this study is at that early stage of developing the method. We think it is possible for these characters of visual flow in each place to be defined one of the design vocabulary for the city space."