Luomahu Lake is a seasonally shallow lake in the northern plain of Suqian City, Jiangsu Province, with an area of 375 km² in 1998, and an average depth of 2.35 m.Based on investigations of possible sources of nitrogen, phosphorus from the basin as well as nutrient outputs in the Luomahu Lake basin, 1998, some estimates are drawn as follows.The total nutrients inputted to the lake are nitrogen 15764.78 t/a and phosphorus 10335.53 t/a, coming separately from its inlets (nitrogen 13598.05 t/a, phosphorus 942.35 t/a), land runoff (nitrogen 25.04 t/a, phosphorus 4.77 t/a), cage aquaculture and artificial food (nitrogen 304.05 t/a, phosphorus 48.06 t/a), release from the sediments (nitrogen 1170.90 t/a, phosphorus 12.64 t/a)and atmospheric precipitation (nitrogen 666.74 t/a, phosphorus 27.71 t/a).The total nutrients drained are nitrogen 14232.13 t/a and phosphorus 813.90 t/a, i. e. from output through rivers (nitrogen 12915.74 t/a, phosphorus 701.56 t/a), harvest of fish (nitrogen 223.12 t/a, phosphorus 57.72 t/a), harvest of aquatic plants (nitrogen 120.00 t/a, phosphorus 21.00 t/a), irrigation and factory utilization around the lake (nitrogen 973.27 t/a, phosphorus 33.62 t/a), respectively.The nutrient balance results shows that the main input and output ways of nitrogen and phosphorus are rivers, the nitrogen input by rivers occupies 86.3% of total input and phosphorus input 91.0%.Nutrient deposit is smaller, with nitrogen deposits 205.47 t/a (deposit efficient 0.097)and the phosphorus deposits 199.95 t/a (deposit efficient 0.214).The nutrient load is much higher, i. e. nitrogen is 42.04 g/(m²·a)and phosphorus 23.76 g/(m²·a).Nevertheless, the concentrations of nitrogen and phosphorus in lake increased quickly in 1998.The main countermeasures of eutrophication controlled are reducing the nutrients from rivers and protecting the aquatic plants in Luomahu Lake.