Abstract: The Comprehensive Nuclear-Test-Ban Treaty (CTBT) International Monitoring System (IMS) radionuclide network, including 80 stations, was designed to monitor nuclear test all over the word. The stations should be certified by CTBT to comply with the technical requirements. Among the certification tests carried out at each station, parallel sampling with portable particle sampler is performed. The verification samples from the portable air sampler will be analyzed at radionuclide laboratories to calibrate the equipments of stations. According to technical requirement of radionuclide station certification, this article deduced the formula of ⁷Be radioactivity concentration. The preparation and analysis procedure of verification samples were established. As part of certification of radionuclide stations RN42 and RN56, the verification samples from these two stations were measured by HPGe γ spectrometer in Beijing Radionuclide Laboratory.