In order to solve the problem of lake eutrophication in Lake Erhai,a model based on the analysis of nutrients transport was applied to establish society,economy,technology and environment coupling SD model for Lake Erhai drainage area using VENSIM-DSS.The SD model is consisted of seven subsystems searching for the sources of TN and TP.The research established a set of parameters applicable for the Lake Erhai coupling model.The stimulation results showed 88% of TN was from the subsystems of plantation,animal husbandry,sewage and dry and wet deposition,and 89% of TP was from the subsystems of plantation,animal husbandry,sewage,soil and water loss in Lake Erhai catchment.Based on the results,four kinds of nutrient reduction solutions were set to stimulate the changes of TN and TP for the next ten years.The feasibilities of different reduction solutions were quantitatively estimated by policy evaluation subsystem and DILLON model to put forward the optimal nutrient reduction solutions for Lake Erhai catchment.