Through systematic sampling and analysis of brine and solids in the salt fields of mining areas Ⅰ and Ⅱ of Qarhan Salt Lake, it is found that the main and trace elements in the brine show different degrees of enrichment in the process of spreading in the salt fields. In addition to salt formation, there are also isomorphism, mother liquor entrainment and other phenomena. Among them, the enrichment rule of rubidium and cesium elements is related to the precipitation of carnallite. The XRD and TOF-SIMS analysis results show that rubidium exhibits a stronger positive correlation with potassium and a negative correlation with sodium, indicating the existence of isomorphism between rubidium and potassium elements. The phenomenon of isomorphism between cesium and potassium elements is not obvious, and it may mainly enter the salt sample through mother liquor entrainment. This research reveals the enrichment patterns and occurrence forms of rubidium and cesium elements in brine, which has certain reference significance for the comprehensive utilization and development of rubidium and cesium resources in salt lakes.