Abstract: The accurate measurement of ²²⁰Rn is important for dosimetry evaluation of natural radiation exposure. The detection efficiencies of normal scintillation cell to different energy α particles decayed from ²²²Rn, ²²⁰Rn and their daughters are different for the large volume of normal scintillation cell. It was proposed that the range of α particles with minimum energy decayed from ²²²Rn could be longer than the longest distance between any two points in the scintillation cell by reducing the air pressure of scintillation cell. Thus, the detection efficiencies of the low-pressure scintillation cell to α particles decayed from ²²²Rn, ²²⁰Rn and their daughters are same. The detection efficiency of low-pressure scintillation cell to α particles can be obtained by standard radon chamber, and then the ²²⁰Rn concentration reference value can be determined by low-pressure scintillation cell.