In the 21st century, the significant advances in the measurement of nitrogen and oxygen isotopic compositions of nitrate are the development of analytical techniques of the denitrifier method. The method has many advantages, such as simultaneous analysis of nitrogen and oxygen isotopic compositions of samples with low NO₃^- concentrations down to μg/L, relief from complicated sample pretreatment, a large reduction in analysis time, only conversion of NO₃^- in samples to N₂O in complex solutions and so on. The experimental procedure consists of several key steps including bacterium selection and cultivation, conversion of sample NO₃^- to N₂O, extraction and isotopic analysis of N₂O and correction of isotopic analytical results. Results from foreign researchers showed that the technique was applicable for the measurement from soil, seawater and freshwater, and was widely used. This technique was also developed in and obtained important advances in the contamination study of nitrate in the vadose zone and groundwater. Because of its advanced analytical technique, We suggest great efforts be given to its research and application in China. Concerned agencies in charge should give more support to the study so that the technique can be modified further and applied widely.