Abstract: Caohai,part of Dianchi in Yunnan Province, is heavily polluted by the discharge of urbanwater water,lost its water body function, and thus threatened the water source of Kuming City. In order to control water pollution in Caohai,comprehensive series of tehcnologies,such as transformation of urban drainage and treatment system, treatment of main undustrial waste water, treatment of area pollution source dredge up of river silt in Caohai,on site clear away technology of polluants, recovery technology of large aquatic plants,and reasonaable management of water resources,are put forward,and short term plan, mid term plan and long term plan for Caohai and Dianchi are formulated. Total investment for these plans is expected to be about 3 billion Yuan RMB.