‘Soil water reservoir' was defined as a space that reserve and transport the soil water in the soil, and total pore space of the soil as maximum available volume of the reservoir. The volume of pore space and the water transportation capability of soil are two of the important reservoir characteristics. In this paper, the efficiency of the ‘soil water reservoir' on flooding control were studied by simulator rainfall in the south of China with 5 typical ecological patterns of red soils, such as sparse wood (Ⅰ), wood-grasses (Ⅱ), grasses-brushwood (Ⅲ), economic orchard (Ⅳ), crop land (Ⅴ), and bare land (Ⅵ) as contrast. Water balance factors of soils were measured and estimated respectively in the experiments, such as rainfall (P), water in-come (F), water reserved (W) in soil, water discharged (D), surface runoff (R) and soil maximum saturated infiltration (F'). Results show that a main obstructive factor resulted in that ‘soil water reservoir' decreased the capacity of flooding control in the red soil area, is that the channel, through which water come into soil, was blocked or partly blocked. The grasses-brushwood (Ⅲ) is the most efficient one of 5 patterns to control flooding, the economic orchard (Ⅳ) pattern is suggested to be used in the area as the first one in sequence because of not only with higher efficiency of flooding control but with higher economic benefits. It is necessary to improve the efficiency of soil's flooding control in the area by protecting wood grasses and brushwood grasses from damage, recovering wood and grasses land from crop, increasing degree of surface grasses-cover in the sparse wood. The results also show that the soil water reservoir theory is available to be used to assess the flooding control function of soils. Capabilities of the ‘soil water reservoir', including soil water reserve and water transport, are most important when we study on ‘soil water reservoir' to control flooding. How to increase soil infiltration? It is a key to improve efficiency of the reservoir on control flooding.