Abstract: This research focuses on the optimization of analysis conditions for ⁹⁰Sr in water sample using extraction chromatography method by di-(2-ethylhexy) phosphoric acid based on GB 6766—1986, and makes this method more suitable for ⁹⁰Sr analysis in environmental water samples with the specific activity lower than 10 mBq/L. In optimized analysis process the P204 resin column was used in separating ⁹⁰Y from ⁹⁰Sr-⁹⁰Y mixture, and the sampling volume as well as the β counting time for the measurements of water samples, detecting efficiency, calibration with electroplating source were optimized. The measurement of ⁹⁰Sr content in an actual low-level environmental water sample was performed, by optimized extraction chromatography method, and the results showed that the full process recovery was 89.8%-124.0% and the detecting limit to ⁹⁰Sr was 0.36 mBq/L, which was lower than 10 mBq/L in GB 6766—1986.