Abstract: This paper presents physicochemical properties of water and their seasonal changes during April,1987-October,1989, in Sanhulianjiang Reservoir.The result are summarized as follows(data as means): 1. The normal conditions of water quality were:Water temperature-18.5,Secchi transparency(cm) 313,pH value-7.80,conductivity(us/cm)-129,dissolved oxygen(mg/ L) 8.81,chemical oxygen demand(mg/L) 2.43,hardness(Germany degree) 3.79,alkalinity(as CaCO3,mg/L) 62.56. 2. Main ionic contents(mg/L)were:calcium-1960,magnesium-3.73,bicarbonate(carbonate) 76.55,sulphate-9.71,chloride-4.77,total ionic amounts-121.82,the water type belongs to CCaⅡ. 3. The contents of main nutrient elements(mg/L)were:nitritenitrogen-0.007,nitrate nitrogen 0.131,ammonia nitrogen-0.379,total nitrogen-1.38,phosphate-0.006,total phosphorus 0.022,silica-2.12. 4. There were marked seasonal changes in most physicochemical components in the water. Also,there were conspicuous differences in horizontal distribution of most physicochemical components.The differences of most physicochemical components were inconspicuous in different years. 5. Sanhulianjiang Reservoir has good water quality and high potential for fish development. However,the N/P ratio was 62.7:1,which means that phosphorus was the major nutrient limiting biological productivity.