Water-body in Fuzhou downstream section of Minjiang River and soil water of wetland growing Cyperus malaccensis in intertidal region of estuary were selected as object of study. The contents of nitrate nitrogen(NO₃-N), nitrite nitrogen(NO₂-N) and ammonium nitrogen(NH₄⁺-N) in the samples were measured by SAN⁺⁺ Continuous Flow Analytical System for showing the difference of their contents between spring and autumn, and the influence of N contents in river water on the contents of soil water. The result showed that:(1) The contents of NH₄⁺-N and NO₃-N in river water in autumn are higher than in spring, and the content of NO₂-N was opposite; In the soil water, the contents of NH₄⁺-N and NO₂-N in autumn were higher than in spring, and the content of NO₃-N was invers; the content of NH₄⁺-N in soil water was higher than that in river water, on the contrary, the contents of NO₃-N and NO₂-N in soil water were less than that in river water;(2) River water was the main source for N in wetland soil water due to submersion of river water influencing on N content of the soil water significantly;(3) The total contents of NO₃-N, NO₂-N and NH₄⁺-N in river water in autumn were more than in spring, there was a obvious seasonal difference;(4) Compared with the contents in river water from Minjiang River in 2007-2008, the N contents in river water increased sharply in recent years, as a result, the river water eutrophication was aggravated.