Abstract: The decomposition rate of Chaetomorpha sp.at different conditions and the release discipline of nutrients from the algal issue were studied in laboratory.The aim of this study was to explain the potential influence of Chaetomorpha decomposition on water quality in Swan Lake.The results showed that the decomposition rate of Chaetomorpha was significantly influenced by temperature (P < 0.01), and high temperature (30℃) could promote the decomposition.However, the effects of sediment and nutrient level on algal decomposition were relatively small.During the early decomposition (0~7 d), the decomposition rate was large and a lot of phosphorus in algal issue was released into the water, while the nitrogen release was slow and last for a long time.The highest release rate of phosphorus reached to 91.63%, while the highest nitrogen release rate just reached to 73.01%.The release rate of nitrogen and phosphorus was obviously influenced by temperature and sediments (P < 0.01).The effects of different factors on phosphorus release followed the order of temperature >sediment >nutrient level, while that of nitrogen release was sediment >temperature >nutrient level.The release rate of nitrogen and phosphorus was both higher on high temperature conditions.Therefore, the dying Chaetomorpha should be removed in time to avoid the deterioration of water quality and secondary pollution in the early autumn.