Abstract: After the cathode materials of spent lithium-ion battery have been leached, valuable metals such as nickel and cobalt in solution are easily recycled, but there's been no good way to recycle lithium. In fact, this leaching solution is similar to Salt Lake Brine, the difference is that the concentration of lithium in the Brine is lower, and there is a large amount of sodium chloride, magnesium chloride associated in the Brine. We can treat the leaching solution as a special "Salt Lake Brine", adjusting its chlorine concentration, and then the widely accepted method for extracting lithium from Salt Lake Brine can be successfully applied. With tributyl phosphate (TBP) used as the extractant, sulfonated kerosene as the diluent and ferric chloride (FeCl₃) as the co-extractant, lithium is selectively extracted. TBP firstly reacts with the acidic solution of FeCl₃-NaCl to form the exclusive extractant for lithium. Then adjust the concentration of NaCl in the leaching solution to more than 250 g/L and conduct the extraction experiment for 5 minutes at room temperature with the organic/aqueous volume ratio (O/A) of 3. It turns out that the extraction rate of single-stage lithium stands at 75 %, while Ni²⁺, Co²⁺ and Mn²⁺ are hardly extracted. According to the equilibrium isotherm, extraction rate of lithium can reach 99 % through four-stage countercurrent extraction.