Abstract: In order to achieve automatic measurement of radon exhalation rate in building materials, an active carbon adsorption-liquid scintillation method was introduced. By comparing the measurement results of this method with the active carbon absorption-γ energy spectrum method on the surfaces of the radon exhalation standard device, uranium ore brick and foaming, the accuracy of this method was verified. The results show that the active carbon adsorption-liquid scintillation method can ignore the effect of back-diffusion under certain conditions. Based on the C-LS-Rn standard source, the calibration coefficient of this method is 72.36 min^-1•Bq^-1. The counting efficiency of radon is 120% by this method. The minimum detectable radon exhalation rate is 8.15×10^-4 Bq/(m²•s) when cumulative time is 72 h. The relative deviation of measurement results between these two methods is about 10%, within the acceptable range.