Abstract: The ammoniumzinccadmium reduction method was used to convert nitrate to nitrous oxide for nitrogen and oxygen isotopic abundance analysis. In water reaction system with pH between 6 and 8, the efficiencies of nitrate reduction to nitrite were above 95%, and the efficiencies of nitrite to nitrous oxide using sodium azide in acetic acid buffer were higher than 99%. An excellent correlation between the known δ¹⁵N and δ¹⁸O values of nitrate and the measured δ¹⁵N and δ¹⁸O values of nitrous oxide exhibited a slope of 0.48 for nitrogen and 0.70 for oxygen, respectively, with both R² values of 0.999 8. The standard deviations of δ¹⁵N of 5 nitrogen compositions of N₂O were between 0.18‰ and 0.43‰ (n=5). The standard deviations of δ¹⁸O were between 0.27‰ and 0.46‰ (n=5). The results show that the precision and accuracy of the test for determination nitrogen and oxygen isotopes of nitrate are the same with other chemical conversion methods. Meanwhile, the data of nitrate nitrogen and oxygen isotopes of different types of water samples meet the experimental requirements. Furthermore the experimental process is also simpler and more efficient with advantage of lower cost.