The plain lakes in Xinjiang have changed a great deal as a result of human's activities. Besides that some of them have become smaller or dried up, water salinzization of the lakes gives rise to a very conspicuous problem either. For example, the water mineralization of the Bosten Lake, the largest interior freshwater lake in China, raised from 0.25-0.40g/l in 1958 to 1.80-1.90g/l in 1986 and this freshwater lake has changed into a saltwater one to a certain extent. The water mineralization of other lakes such as the Buluntuo Lake and the Ailike Lake has increased notably. The water salinization of plain reservoirs is becoming more and more serious from day to day. The water salinization of lakes and reservoirs could exert an unpleasant influence on fishing, irrigation, reed growth, drinking water, and people's health. It is mainly the deterioration of salt balance and water balance that resulted in the water salinization. For the prevention and control of the water salinization, we have to drain less farm fields water into the natural river courses and lakes in order to ensure the water supply for ecologic purpose and put an end to the loss state in which the water balance of lakes has been for a long time.