Abstract: Jiangling sunken area is located in the southwest of Jianghan basin of Hubei province，which is abundant in potassium-rich brine with higher temperature and pressure，the total salinity of the brine reaches about 336.98 mg/L，mainly including sodium chloride，potassium chloride，and other trace elements（such as lithium，rubidium，and cesium）.And the mass concentration of Rb+ reaches 80 mg/L，that is rich enough to be commercially mined. Potassium and rubidium are accompanying elements.During the sodium extraction of evaporation-and-concentration and potassium leaching of cooling crystallization processes，rubidium is enriched in the mother liquor.Experimental results showed that rubidium could not be enriched at the same enrichment rate with other trace elements，its enrichment rate is low，and the loss is serious with a loss rate of 12.28%.The potassium-rich brine collected from Jiangling sunken area was used to study the losing mechanism of rubidium during potassium crystallization，and the results showed that the main reasons of rubidium loss as follows：the loss rate by isomorphism was 9.66%，the loss rate by crystal inclusion was 1.71%，and the loss rate by mother liquor entrainment was 0.91% .

Key words: potassium-rich brine, rubidium, isomorphism, crystal inclusion, potassium leaching of cooling crystallization