The principle of the method specified is dissolving a test portion in hydrochloric and nitric acids, fusing the acid-insoluble residue with sodium carbonate, adding potassium chloride/lanthanum nitrate solution as a spectrochemical buffer, spraying the solution into a dinitrogen monoxide-acetylen flame, and spectrometrically measuring the atomic absorption of the 422,7 nm spectral line emitted by a calcium hollow cathode lamp. The method is applicable to calcium contents betwen 0,0005 % (m/m) and 0,005 % (m/m).