Trimethly benzyl ammonia chloride (TMBAC) and potassium sulfocyanate were used as complexants of cobalt. Co ⁿ⁺ and Vitamin B ₁₂ were separated by exacting (TMBAC)-Co ⁿ⁺- SCN^- into chloroform. Under a suitable acidity condition,when basal body improver was added Coⁿ⁺ and Coⁿ⁺ combined with Vitamin B ₁₂ were determined by graphite furnace atomic absorption spectrometry (GFAAS).The separation of Coⁿ⁺ and Vitamin B₁₂ was effective because Vitamin B₁₂ can not be dissolved in chloroform and can not be combined with TMBAC.The method was economic , easy and better than others.