【Objective】NO₂^- is a key intermediate product of several nitrogen transformation processes in soil, with low concentration and fast transformation. The combination of denitrifier method and mass spectrometry technology has been widely used in the ¹⁵N isotope analysis of NO₃^- or NO₂^- in water. 【Method】This paper aims to optimize the culture and reaction conditions of Stenotrophomonas nitritireducens denitrifier method, and to realize the specific, rapid and accurate determination of NO₂^--¹⁵N abundance in soil extract. Thus, we will optimize the culture method and reaction conditions, and bacterial concentration of denitrifier method, then applied this method to the soil extract. 【Result】There was no significant difference in the ¹⁵N isotopic determination of NO₂^- samples between aerobic shaking with seed solution and microaerobic incubation of single colonies. The seed solution ensures the stability of different batches of bacteria and aerobic incubation reduces the incubation time from 7~8 days to 12~15 h. High purity N₂ or He purging for 0.5 h can effectively remove O₂ and blank nitrogen, but the cost of N₂ purging is lower. The transfer of N₂O gas to the dry gas cylinder did not affect the accuracy and precision of the determination results. However, it can prolong the sample preservation time and reduce alkali steam corrosion of the instrument pipeline. Also, using bacteria in logarithmic growth phase and adjusting the reaction system to an OD₆₀₀ value of 0.3~0.9 will ensure their denitrification efficiency and reduce variation between batches. Using no more than 1 mol·L^-1 KCl to extract the soil will ensure the extraction efficiency and reduce the impact on the viability of the bacteria.【Conclusion】The optimized method can accurately determine the ¹⁵N abundance of NO₂^- in different types of soil with a measurement accuracy of δ¹⁵N of 5~20 nmol and natural abundance value of NO₂^- between 0.1‰~0.9‰, with most values being less than 0.5. Also, the experimental period was greatly shortened, simplified steps and save cost.