The invention relates to a method for extracting 
lithium from an 
alumina production process and preparing battery-grade 
lithium carbonate. The method comprises the following steps of: cooling a refined solution, and carrying out a reaction with an acidic compound to prepare an aluminum 
hydroxide active 
seed crystal; then, mixing the active 
seed crystal with a 
sodium aluminate solution to enrich 
lithium in the 
sodium aluminate solution to obtain lithium-rich aluminum 
hydroxide; mixing the lithium-rich aluminum 
hydroxide and an 
organic acid to carry out a 
microwave desorption reaction, and carrying out 
solid-liquid separation after the reaction is completed, wherein the 
solid is lithium-free aluminum hydroxide and the liquid is lithium-rich 
desorption liquid; adding alkali liquor to the lithium-rich 
desorption solution to adjust the pH value, and adding a lithium purification inhibition agent to remove aluminum ions, iron ions, 
calcium ions and 
magnesium ions to obtain a lithium-rich refined solution; and adding a saturated 
sodium carbonate solution to the lithium-rich refined solution to precipitate lithium to obtain crude 
lithium carbonate, and repeatedly the washing crude lithiumcarbonate with high-purity water to obtain the battery-grade 
lithium carbonate. The method realizes high-efficiency high-quality extraction of lithium in the 
alumina production process, and is in seamless connection with the existing 
alumina production process. The method has a simple process and low production cost and is suitable for industrial promotion.