As part of the series studies on ecological restoration technique in the littoral zone of Dianehi Lake, Yunnan Province, this paper revealed the state and cause of environmental depravation and ecological degradation in the North-East littoral zone of Dianchi Lake, and discussed the key obstacle factor for natural restoration.Dianchi Lake is one of the most seriously polluted lakes in the world.Surely the wastewater discharge is the main cause, but another cause is usually ignored, that is the ecological destruction of the littoral zones which ever played a very important role in pollutant degradation and sedimentation.The wetland around the lake has been cut off by constructed concrete dikes, which enhanced wave action in front of the dike and therefore caused soil erosion and destruction of the littoral zone ecosystem.In addition to serious water pollution, all the macrophytes and benthic invertebrate animals have disappeared from the littoral zone.It has become "desert in the water.The construction of the concrete dike around the lake and pollution are the causes of environmental depravation and ecological degradation in the littoral zone, and wave erosion is the key obstacle for natural restoration.Hence, special ecological engineering technique is urgently needed to restore the littoral zone environment and ecosystem in such a lake.