The hydrogenation and pyrolysis of this process are both continuous operations. Firstly, industrial grade lithium carbonate is mixed with pure water and returned mother liquor in a certain proportion to form a slurry, which is then pumped to a continuous hydrogenation tower. Carbon dioxide gas is introduced into the hydrogenation tower and hydrogenated at a certain pressure and temperature to obtain a lithium bicarbonate solution. The hydrogenated solution is then filtered by a filter press and precision filtration, and then enters the resin impurity removal system for impurity removal. After impurity removal, the liquid is pumped into the continuous pyrolysis tower for pyrolysis, and the pyrolysis solution is further separated by centrifugation in a centrifuge. The wet material separated by centrifugation is dried, screened, iron removed, crushed, and packaged to obtain high-purity lithium carbonate products. Part of the pyrolysis mother liquor is returned to the mixing tank for mixing, while the remaining part is extracted and processed separately. The carbon dioxide pyrolyzed by the pyrolysis system enters the carbon dioxide recovery device for recovery, and the recovered carbon dioxide is then returned to the hydrogenation system for reuse.