The invention discloses enrichment and separation of three heavy metal ions, namely copper, cadmium and lead, in a digested tea oil sample solution through a solid phase extraction pillar of a hydroxylated multi-wall carbon nano tube. By the strong selectivity adsorption capacity of the hydroxylated multi-wall carbon nano tube to the three heavy metal ions, relatively low detection lower limit and relatively high enrichment capacity can be obtained. A flame atomic absorption spectrophotometer can be fully used for measuring trace copper, cadmium and lead ions in the tea oil, and is high in selectivity, high in adaptability and high in analysis speed; compared with the cost of other analyzers, the cost of the spectrophotometer is greatly reduced.