Abstract: The method determining the specific radioactivity of ~(90)Sr in high-level liquid waste is set up. It is composed of extraction with 0.5 mol/l HDEHP-n-heptane RE from 0.1 mol/l HNO_3 aqueous solution. extraction Sr from the aqueous solution which acidity was adjusted to pH6. 3—6.5 by adding NaOH and NH_4Ac-HAc buffer with 0.1 mol/I PMBP-1 mol/I TBP-Xylene. reextraction Sr from the organic phase with 6％ HCOONa-HCOOH, clearing RE with Fe(OH)_3 precipittor and counting the counts of~(90) Y of Y_2(C_2O_4)_3 from which calculating the radioactivity of ~(90)Sr.