The subject of center of gravity is inseparable from our daily lives; hence, the research on center of gravity has very important practical significance. This paper mainly studies the change of the center of gravity of a cuboid containing two water tanks upon flipping. Using the idea of differential equations, Visio and RealFlow are used to simulate the entire process, and the influence on the distance between the centroid and the center of gravity of the cuboid (including the water tanks) caused by the proportion of water in the water tank is studied and the inclination angle of the water tank is calculated via integration. By establishing a model through differential equations, the change of the center of gravity is studied when the cuboid (including the water tanks) is flipped.