Abstract: In the process of decommissioning of nuclear facilities, the nondestructive measurement of transuranic nuclide radioactive samples is generally realized by gamma spectrometry. However, the detection limit of this measurement method is high and it is not suitable for the measurement of low-level radioactive samples after dissolution because the probability of transuranic nuclide gamma ray emission is generally low. The method based on large area flow gas ionization chamber was established in this work and  can be used for indirect nondestructive measurement of surface irregular samples by detecting the principle of α particle ionized air. The detection limit of the method is low, and the sample plate with radioactivity as low as 100 Bq can be analyzed.