Abstract: The paddy rice areas in the Three-River-Plain has reached 0.95 million hectares, accounting for 28.6% of the total cultivated area, which resulted in the descent of the groundwater, and would make much adverse impact on the swamp and the whole environment. The suitable paddy rice planting areas were estimated based on the Agricultural Water Consumption (AWC) and Groundwater Exploitable Modulus. The primary conclusions are as follows: first, AWC is 483 mm at the present paddy field proportion. The feasible proportion should be 30% if certain runoff is taken into account, and the maximal proportion could be up to 60% if there is no runoff. Second, the essential approaches to enlarge the paddy rice areas are to adopt advanced planting method to reduce water consumption of paddy rice, and to derive water from rivers to increase usable water.