Abstract: Element analysis isotope mass spectrometry technology was applied to determine nitrogen isotope composition of sample from environmental and geological fields. In this work, the effect of suitable conditions for modern soils and loess samples measurement on experimental results were chiefly ascertained through comparisons. Moreover, the negative influences including uncompleted reaction of sample, baseline excursion and the decline of oxidation capacity in soil sample measurement were discussed. The results showed that the measurement precision of nitrogen isotopes can be less than ±0.3‰ with Cr 2O 3/Co 3O 4Ag oxidation furnace, 80—90 mL/min of carrier He flow rate, 84 Pa of Conflo He pressure and 100 mL/min of oxygen injection.