Abstract: Vicia faba root tip was used as material. Micro nuclear technology of root tip cell of Vicia faba was applied to study Genetoxic of Vicia faba root tip cell under different concentration single lead and mercury and combination with ascorbic acid treatment. The result showed that the mitotic index has rising trend with 5 mg/L and 10 mg/L of Pb2+ concentration. Whlie it has downward trend, when Pb2+ concentration is over 10 mg/L. While Hg2+ concentration is low or high, mitosis index was reduced. Chromosome aberration rate and micronucleus rate were positively correlated of concentration of Pb2+ and Hg2+. After Vicia faba root tip cell was treat by ascorbic acid conbination with different concentrations of lead ion and mercury ions, it showed obvious synergy and relieve genetic toxic effect. Especially in high concentration of heavy metal stression, remission effect is relatively obvious.