In order to explore the influence of sandstone architecture on waterflooding mechanisms using the architecture method, and taking as an example the M-I layer of the Kumkol oilfield in the South Turgay Basin, Kazakhstan, we portrayed the architecture features of different types of sandstones and quantitatively characterized heterogeneities in a single sand body in meandering river facies. Based on the waterflooding characteristics of point bar sand and overbank sand according to waterflooded interpretation results in 367 wells and numerical simulation results of well groups, we finally analyzed the remaining oil potential of the meandering river sandstone and pointed out its development directions at the high water cut stage. The result shows that because lateral accretion shale beds are developed inside single sand bodies, the point bar sand is a semi-connected body. The overbank sand is thin sandstone with poor connectivity, small area and fast lateral changes. The heterogeneity of the overbank sand is stronger than the point bar sand. The sandstone architectures control the waterflooding characteristics. In meandering river sandstones, the bottom of the point bar sand is strongly waterflooded, while the top of the point bar sand and most of the overbank sand are only weakly waterflooded or unflooded. The thickness percentage of unflooded zone and weakly waterflooded zone in point bar sand is 40%, and the remaining oil in its top part is the main direction for future development.