Abstract: The nitrate concentrations in greenhouse soil and the water of Dianchi basin were investigated. Results show that NO^-₃-N concentration in 0～60 cm soil layers increased with the increasing of the age of plastic greenhouse, aggravating soil salinization. There is a significant positive relationship between NO^-₃-N content and total salt concentration in greenhouse soil, the correlation coefficient of the soil lay(0～20 cm) is 0.899^**, the soil lay(20～40 cm) is 0.676^**. There is a positive relationship between the NO^-₃-N concentration in ground water and the NO^-₃-N concentration in greenhouse soils (0～20 cm), the correlation coefficient was 0.945^**, nitrate accumulation in soil has seriously threat to ground water in Dian-lake drainage area. There is a positive relationship between the total N concentration in surface water and the NO^-₃-N concentration in greenhouse soils (0～20 cm), the correlation coefficient is 0.994^**. The accumulation of soil nitrate will aggravate the burthen of non-point source pollution in Dianchi basin.