The invention belongs to the technical field of environmental protection and monitoring and relates to a pretreatment method for measuring nitrogen and oxygen isotopes through a chemical conversion method and a measurement method. The pretreatment method for measuring the nitrogen and oxygen isotopes through the chemical conversion method comprises the step that: low-temperature treatment is carried out on sodium azide-acetic acid buffer solution at a temperature lower than or equal to 15 DEG C. According to the method disclosed by the invention, the low-temperature treatment is carried out on the sodium azide-acetic acid buffer solution at the temperature lower than or equal to 15 DEG C, and therefore, the interference of the sodium azide-acetic acid buffer solution on N2O obtained from the reaction of nitrate in a sample during testing can be greatly decreased, and the precision of a test result can be improved.