【Objective】Atmospheric ammonia (NH₃) is an important precursor for the formation of PM_2.5. Hence, identification and quantification of the sources of atmospheric NH₃ are important for NH₃ emission abatement and air pollution control. Farmland NH₃ volatilization is one of the important sources of atmospheric NH₃. The technology of natural abundance of nitrogen isotopes (δ¹⁵N) has been used to trace NH₃ sources in recent years. Despite these advances, studies on the dynamic change of δ¹⁵N values from the whole process of NH₃ volatilization from farmland soils are lacking. Moreover, NH₃ volatilization from farmland soils is affected by different factors such as soil properties, pH, which can directly or indirectly influence the δ¹⁵N values of volatilized NH₃ and may lead to uncertainties in sources traceability. Upland soil NH₃ volatilization dominates total farmland NH₃ volatilization in China. We selected four types of upland soil from different regions in China to study the δ¹⁵N values of NH₃ volatilization from the whole volatilization process to clarify the changes of δ¹⁵N-NH₃ values and their impacting factors.【Method】Urea was applied to four types of soils from Liaoning, Hebei, Henan and Tibet, and NH₃ volatilization was studied in a 15-day indoor culture experiment by the sponge absorption method under controllable conditions. The δ¹⁵N value during the whole process of NH₃ volatilization was measured by the chemical transformation method.【Result】Results showed that the values of δ¹⁵N during NH₃ volatilization from Beipiao soil from Liaoning Province ranged from -26.14‰ to -5.57‰, with an average of -21.74‰±1.89‰. The variation range of δ¹⁵N values of Xinxiang soil (from Henan province) was from -31.92‰ to -26.31‰, with an average value of -29.31‰±1.72‰ while that of Tangshan soil (from Hebei province) and Linzhi soil (from Tibet) ranged from -24.41‰ to -3.11‰ with an average of -19.82‰±2.04‰, and from -29.17‰ to -2.20‰ with an average of -23.25‰±2.16‰, respectively. Overall, the δ¹⁵N values of the NH₃ volatilization process in upland soils from different regions are different. During the whole process of soil NH₃ volatilization, the δ¹⁵N-NH₃ values of Xinxiang continued to increase, and the δ¹⁵N-NH₃ values of Beipiao, Tangshan and Linzhi first decreased and then increased. Soil properties and NH₃ volatilization rate are the main factors affecting the δ¹⁵N value.【Conclusion】Our results showed that soil pH, NH₃ volatilization rate and cumulative NH₃ loss were significantly negatively correlated with the δ¹⁵N-NH₃ values. In addition, isotope fractionation also impacts the δ¹⁵N-NH₃ values. The results of this study can provide better support for the quantitative traceability of atmospheric NH₃.