"Bojie" brand BMLi lithium resin is a specially designed and synthesized lithium ion screen. Based on the small radius of lithium ions, the special pore structure of the extraction agent can make lithium ions enter the crystal layer, but magnesium, sodium and calcium plasma can not enter, so as to achieve the efficient selective adsorption of lithium ions. The adsorption, desorption and regeneration of lithium extraction agent are carried out at room temperature. For ph5.5-7, the ratio of magnesium to lithium is tens to hundreds. Lithium content in dozens to hundreds of PPM brine has excellent adsorption separation effect.