Over the past few decades,inland lakes unbalanced and their ecological environments were deteriorating due to combined effects of climate change and human activities.At present,to open out systematically the complex relationships and interact rules between factors of lake water balance is an important scientific issue to be tackled.We studied largest inland fresh water lake-Bosten Lake based on system sciences and system dynamic modeling approach using metrological,hydrological and socio-economic data from 1983 to 2013.The results of dynamic water balance analysis,sensitivity analysis and scenario analysis demonstrated that:(1)the variation of lake water level and its environmental change were caused by coupling effect of climate changes and human activities,among which water table declining of Bosten Lake over the decades was mainly due to proliferation of water demand in Konqi River area;(2)the order of most sensitive natural factors to lake water level variation are:surface water inflows>evaporation>surface water outflows;the most sensitive socioeconomic factors to lake water level variation are:irrigation quota>irrigation area> industrial output>population;(3)the scenario analysis in the future 30 years indicate that following tasks have to done:controlling irrigation area,popularization of water-saving technology in agriculture,adjusting industrial structure,effective use of water resources,optimizing water using proportions between the socioeconomic and ecology in order to maintain the water level at a proper level,the ecological environment well, and fulfill the sustainable development of socioeconomic system simultaneous.