Abstract: At present，the separation of magnesium and lithium in sulfate-type salt lakes with high magnesium content is a difficult technical problem.In addition，lithium can′t be highly enriched with the increasing concentration of carbonate ions during exploiting lithium from carbonate-type salt lakes.In this research，the brines from sulfate-type salt lake and carbonate-type salt lake were mixed to separate out large amount of magnesium carbonate trihydrate，so that the magnesium and carbonate ions could be basically removed，and the brine system could be simplified.Therefore，the lithium rich brine could be obtained and high grade lithium carbonate could be separated out by adding sodium carbonate into it.The single lithium yield was over 80%.The method both solved magnesium-lithium separation and lithium enrichment problems of sulfate-type and carbonate-type salt lakes.

Key words: mixed brine, lithium carbonate, salt lake development