The invention relates to a process and a device for extracting battery grade lithium from brine. The process comprises the following steps: adding an adsorbent into the brine to adsorb lithium ions in the brine, intercepting the adsorbent by using a ceramic membrane filter, performing plate-frame pressure filtration on the ceramic membrane concentrated solution to obtain an adsorbent filter cake, washing and desorbing the adsorbent filter cake so as to obtain a desorption solution; removing magnesium in the desorption solution through a nanofiltration membrane system, entering the nanofiltration membrane permeate into an ion exchange resin tower for performing deep magnesium removal, concentrating through a reverse osmosis membrane, performing deep concentration in a DTRO membrane or electrodialysis equipment, evaporating the concentrated solution, adding BaCl2, Na2CO3 and NaOH into the solution, stirring, filtering in a ceramic membrane filter, performing plate-frame pressure filtration on the ceramic membrane filtrate, adding Na2CO3 into the clear liquid, preparing Li2CO3, washing Li2CO3 through a ceramic membrane, centrifuging, and drying, thereby obtaining the finished battery grade Li2CO3 product.