Abstract: Ra, as an alkali native metal, is easily enriched in human skeleton, leading to continuous internal irradiation to the human body, so it is very important to accurately measure the ²²⁶Ra in water samples. ²²⁴Ra was used as chemical tracer, and the α microfiltration source was prepared by preconcentration with Pb(Ra)SO₄, Ba(Ra)SO₄ co-precipitation and vacuum micro-filtration in this study. Water samples with ²²⁶Ra by adding standard solution were measured on α spectrometry. The relative deviation range of the measured value and the actual added value is from 0.4% to 13.1%. This analysis technology can provide a new technical method for the radiation supervision department to quickly monitor the radionuclide ²²⁶Ra.