Battery grade lithium carbonate is the key raw material for the production of cathode materials for lithium-ion batteries. For example, the cathode materials for lithium cobaltate batteries, Lithium iron phosphate battery and ternary batteries are all synthesized on the basis of battery grade lithium carbonate. In addition, battery grade lithium carbonate, as an electrolyte additive of lithium ion battery, can not only significantly improve the safety performance of the battery, but also extend the service life. However, calcium and magnesium ions in the lithium carbonate electrode will block the pores of the ion selective electrode to prevent electrolytic reaction, so it is necessary to detect calcium and magnesium content.