The spatial distribution of the purple soil magnetic susceptibility and the soil particles composition within the water-level-fluctuating zone of the Three Gorges reservoir area in Yangtze River is systematically studied. The characteristics evolution of soil magnetic susceptibility is a key point in the condition of long alternating time of hot, dry, and high-pressure flooding. And next, the distribution of soil particle size is clarified in order to reflect the specific relationship between soil magnetic susceptibility and different sizes. SM-30 portable magnetic susceptibility meter and Bartington MS2 magnetic susceptibility meter are used to determine soil magnetism, and Malvern Mastersizer 2000 laser particle size analyzer is used to derive soil particle volume percentage. After that, the essential reason has been discussed and analyzed based on the relationship between them. It has been demonstrated that firstly, the magnetic susceptibility slowly declines from high level to lower part along different macro-level altitude. And then a rapidly uplift will suddenly happens until more than 120×10-8m3/kg after the stable value area at the middle level. The reason for that is reasonable inferred that the upper slope suffers from the river erosion with high water level, and from the rain erosion with low water level. At the same time, the lower slope is under the control by the consequences of superposition, such as soil accumulation and many other factors.