【Objective】¹⁵N isotope techniques have been widely used in investigating soil and water nitrogen transformation. The ¹⁵N isotopic composition of NO₃^–, NH₄⁺ and N₂O are key data for this type of study. These gas or liquid samples are usually stored before their concentrations or before ¹⁵N abundance are determined. Nevertheless, improper storage processes may induce changes in these samples. However, the effect of storage conditions on the ¹⁵N isotopic composition of the gas or liquid samples has not been well defined. 【Method】The influence of storage container, temperature, sample pretreatment, time and other factors on the ¹⁵N abundance of gaseous and liquid samples were studied in this paper. 【Result】The stable storage time of N₂O samples in aluminum foil air bags is very short, and its δ¹⁵N values significantly changed after 10-day storage. Also, the δ¹⁵N values were stable in a screw-top vacuum vial + butyl septa and clamp headspace vial + butyl septa for about 200 days. For soil extracts with natural abundance, the δ¹⁵N values of NO₃^– kept stable for about 10 days when refrigerated at 4 ℃ and frozen at –20 ℃, but its δ¹⁵N values of NH₄⁺ remained stable for about 60 days and no more than 10 days when frozen at –20 ℃ and refrigerated at 4 ℃, respectively. Besides, for ¹⁵N enriched soil extracts, the ¹⁵N abundance of NO₃^– was stable for about 160 days, while the ¹⁵N abundance of NH₄⁺ was only stable for about 30 days in –20 ℃ and less than 10 days in 4 ℃. For river samples, δ¹⁵N values of NO₃^– and NH₄⁺ were only stable for about 10 days no matter whether the samples were refrigerated at 4 ℃ or frozen at –20 ℃.【Conclusion】 Our results highlight the importance of storage conditions on ¹⁵N abundance of gas and liquid samples, and provides scientific guidance for proper storage conditions when adopting ¹⁵N isotope techniques.