Salt-tolerant superabsorbent polymer (SAP) was synthesized to improve the water retention properties of saline-alkali soil. The Lop Nur saline-alkali soil of Xinjiang with high salinity (total dissolved salt: 18.13wt%) was the object of improvement. The good swelling capacity of SAP (69.04 g/g) under high salinity condition contributed to the superb slow-release water property and further [showed](https://www.wordhippo.com/what-is/another-word-for/build.html) [excellent](https://www.wordhippo.com/what-is/another-word-for/excellent.html) water retention property of SAP-saline-alkali soil (28 days), which showed a good application potential of SAP in saline-alkali land. The swelling mechanism under high salt condition was also explored. Notably, owe to the complexation reaction between and three hydrophilic groups of SAP, the swelling capability of SAP tended to keep steady when the concentration of CaCl ₂ exceeded 0.55wt%. Interestingly, the distribution of the calcium salt in SAP was directly displayed by the maximum intensity projection of computed tomography.