The slag containing lithium phosphate as the recovery product of low concentration lithium containing waste liquid is hardly used as the production raw material of lithium battery due to its high impurity content.In order to make full use of this kind of lithium phosphate slag to alleviate the demand pressure of lithium resources for the rapid development of new energy vehicle industry,according to the large solubility difference between lithium salt and calcium salt under weak acid conditions,acid and soluble calcium salt were added to lithium phosphate to directly realize separation of lithium and phosphorus from lithium phosphate slag under acidic conditions.The effect of acid addition amount,calcium addition amount,pH of conversion end point,conversion liquid-solid ratio and conversion time on lithium conversion efficiency was studied.It was found that the conversion rate of lithium could reach 96.8% when the volume mass ratio of acid addition amount to solid raw material was 1.04 mL/g,calcium addition amount was 0.9 times of the amount of phosphorus in lithium phosphate and the pH end point was 4.0.After pH adjustment,chemical impurity removal and ion exchange depth removal of the converted liq-uid,battery grade lithium carbonate could be prepared by strictly controlling the lithium concentration in the purified liquid,the filtration accuracy of sodium carbonate,the temperature of the reaction system.The product contained the main component of about 99.65%,with the impurity content up to the requirements of YS/T 582—2013.The comprehensive recovery of lithium was 93.4%.