The invention discloses a method and device for test detection of degassing factors of a degassing tower of a nuclear power plant. The method for test detection of the degassing factors of the degassing tower of the nuclear power plant comprises the following steps of S1, dissolving simulation gases in simulation material liquid to simulate radioactive raw material liquid, wherein the simulation material liquid is a solution which contains boric acid in a dissolved mode, the simulation gases comprise N2, O2 and a stable isotope Xe, and the Xe is a tracer element; (2) injecting the simulation material liquid with the simulation gases in a dissolved mode into the degassing tower to carry out degassing; (3) using the simulation material liquid discharged from the degassing tower after the degassing as tower bottom material liquid, measuring the concentration of the Xe in the tower bottom material liquid, and calculating the degassing factors of the degassing tower. The device for test detection of the degassing factors of the degassing tower of the nuclear power plant comprises a mass spectrometer, a feed liquid tank, a gas-liquid mixer, the degassing tower and a sampler, wherein the feed liquid tank, the gas-liquid mixer, the degassing tower and the sampler are connected in sequence. The method and device for test detection of the degassing factors of the degassing tower of the nuclear power plant have the advantages of being good in economy of detection of the degassing factors of the degassing tower, free of radioactive hazards, and capable of protecting the environment.