The effects of different cropping systems on content of nitric nitrogen in soils were studied. The results indicated that, there is more nitric nitrogen in vegetable soils in green-houses, followed by opened vegetable soils, and then traditional vegetable soils, the lowest nitrates were found in paddy soils. Moreover, the over-application of large amount of nitrogen fertilizers resulted in soil pH decrease. Statistical analysis showed that there is a significant negative correlation between Ph (y) and content of nitric nitrogen (x) in the soils (y=-9.961x+98.095 R²=0.151 n=84).