The process of eutrophication was studied in the lake Changja from November in 1974 to May in 1975. The stratification of water temperature was going to be formed in April and the content of dissolved oxygen varied a little but it was almost zero from January. Total phosphorus was increased very rapidly in February but total nitrogen and carbohydrate-like substances were increased a little during the experimental period. The amount of chlorophyll-$alpha$ varied from 127mg/$m^2$ to 717 mg/$m^2$ with maximum value occuring in January. This phenomenon was an evidence that chlorophyll-$m^2$ and total phosphorus were correlated each other. The numbers of colony of the coliform bacteria in point A was 10 times more than in point B. In conclcesions, the lake Changja is a very eutrophic and the ecological equilibrium of the lake can not be recovered as far as origin of pollution is erased out.