Background: Radon is one radioactive gas which should be monitored.Purpose: High sensitivity

good stability for distinguishing the characteristics of radon and thorium in air radon content measurement are required.Methods: One alpha energy spectrum measuring device was designed based on diffusion-accumulation theory.And the major influence factors were discussed.At the same time

the preliminary solution was proposed and testing was progressed.Results: We have got the results of energy calibration curve

energy resolution

sensitivity and other important information by standard radon chamber calibration.Conclusions: The experimental results show that this scheme is feasible and the performance is suited to the national standards for air radon measurement requirements.