Abstract: The decaying process of submerged macrophytes (Vallisneria spiralis, Myriophyllum verticillatum Linn) and the nutrition release during this process were investigated in simulating condition. The results indicated that Vallisneria spiralis and Myriophyllum verticillatum Linn decayed in cold weather. During this process, they released a little nutrition to water and most of the nutritionwas kept in the remains of the plant. While the weather grew warmer next year, the decaying of plants became faster and nitrogen and phosphorus would be released to water while some would come into sediments. The decay rates of Vallisneria spiralis and Myriophyllum verticillatum Linn were comparatively low, and this would lower the cycling rates of the nutrition in the system. Quantities of plants' remains could affect the decaying speed and extend of plants. Water would become anoxic when there were abundant plant remains and thus result in quick decaying of plants, which would cause deterioration of water quality.〖WTHZ〗Key words: 〖WTBZ〗〖ZK(〗submerged macrophyte; decay; nutrition release