Based on the investigation and analysis of hydrology and water resources in Shanwei area, one water resources optimal allocation simulation model supported by MIKE BASIN digital platform is built up. Under the condition of different guarantee rate, recommended program of water demand and recommended program of water supply in Baseline year and planning year 2020, using river, reservoir, pool as source of water supply, adopting four grades of county drainage area as arithmetic element to make separate analysis of the balance between demand and supply on the source of water, therefore the most optimum distribution will be achieved for domestic water of town and country, industrial water, irrigation water and ecology water, the allocation results satisfy all kinds of water needs in the planning years in Shanwei.