In this paper, the polluted sediment capping technique was used to control the eutrophic water from the Dianchi Lake on the basis of field simulating experiments. The capping experimental materials include natural laterite and additives such as coal ash and powder of lime, which are all cheap geological materials. An analysis of the 125-day monitoring data consisting of the physical and chemistry indexes showed the eutrophication of the experimental barrel water and the interrelated water, it is held that the application of natural mineral materials to controlling the water eutrophication through the reduction of the internal pollutant loading of the polluted sediments in the eutrophic lake or reservoir is an effective technique, and that the laterite is an efficient superstratum for separating the polluted sediments from the upper eutrophic water. It is also considered that laterite plays an important role in reducing the release of the total phosphorus and the total nitrogen and increasing the controlling efficiency of the breeding and floating of the phytoplanktons such as alga, algae cells and algae embryos by means of the addition of the additives like coal ash and powder of lime. The algae may be eventually eliminated from the water. The technique can provide a new train of thought for the remedy of the eutrophic water in the Dianchi Lake and similar lakes.