Abstract: Total nitrogen (TN) of 24 sediment samples was determined in this paper by Kelvin digestion-macro-sample distillation-Nessler's reagent colorimetric method (Kelvin method) and potassium persulfate digestion method. It was found that the contents of TN measured by kelvin method were lower than those of potassium persulfate digestion. That was because the contents of nitrate nitrogen and nitrite nitrogen did not include the results determined by Kelvin method. It also showed that determination results from two methods showed characteristics of high positive correlation, and its correlation coefficient reached 0.928(Sig < 0.01). Because potassium persulfate digestion method was simple and the cost of the method is low, the determination results were more reliable; therefore, it can be used to measure TN of soils in water-level-fluctuating zone.