Abstract: Radioactivity purity of the solid ²¹⁹Rn source made using ²²⁷Ac extracted from uranium ore were determined by γ-spectrometry. The activities of ²²⁷Th, ²²³Ra, ²¹⁹Rn and ²¹¹Bi produced by the decay of ²²⁷Ac and the contents of ²²⁶Ra, ²²⁴Ra which generates ²²²Rn, ²²⁰Rn to affect the purity of actinide in this source were analyzed after ²²⁷Ac in radioactive equilibrium with its daughter nuclides. The γ-ray energy used for the determination of these daughter nuclides of ²²⁷Ac are 235.97, 256.25 keV for ²²⁷Th, 154.21 keV for ²²³Ra, 401.81 keV for ²¹⁹Rn, and 351.059 keV for ²¹¹Bi. Through the analysis, the results are acquired that their activities are (1 069±3), (1 079±5), (1 095±13), (1 096±14) and (11 089±4) Bq respectively, and the average activity of solid ²¹⁹Rn source is (1 093±8) Bq. The activities of ²²⁶Ra and ²²⁴Ra in this source are 5.12 Bq and 0.433 Bq respectively by the γ-ray energy as follows: 238.632 keV of ²¹²Pb, 583.191 keV of ²⁰⁸Tl for ²²⁴Ra, and 609.312, 1 120.287 keV of ²¹⁴Bi for ²²⁶Ra, as they are all far below (1 093±8) Bq, so the radioactivity purity of the solid ²¹⁹Rn source is very high. The results show that the solid ²¹⁹Rn source can be developed to the standards for the efficiency calibration of the delayed coincidence counting system.