The invention relates to the technical field of chemical detection and analysis of nuclear power plants, and discloses a method for measuring the activity concentration of gaseous carbon 14 in a nuclear power plant environment. The method comprises: collecting an air sample, and fixing a carbon element in the air sample to a carbonate; converting the carbonate into solid calcium carbonate by pretreatment, and grinding the solid calcium carbonate into a specified mesh number to obtain a calcium carbonate powder solid; weighing the calcium carbonate powder solid of a specified mass into a samplebottle, adding a first specified volume of demineralized water and a second specified volume of scintillation liquid, and shaking uniformly to obtain a sample to be tested; cooling the sample to be tested, placing in a liquid scintillation spectrometer, and placing in dark to avoid light; and after the sample to be tested is stood for a first specified time length, measuring a counting rate of the sample to be tested. By the method for measuring the activity concentration of gaseous carbon 14 in a nuclear power plant environment, the sample obtained has good stability, and the stability of activity concentration measurement of the gaseous carbon 14 in the environment can be improved.