Abstract: The toxicity of Cd²⁺and its combination with surfactant or simulated acid rain to Vicia faba root tip cell was studied by using micro-nucleus technique. The results showed that the formation of micro-nucleus in Vicia faba root tip cell was strongly induced by Cd²⁺ in its concentration of 0～10.0 mg·L^-1. The micro-nucleus rate was 13.85‰ at 6.0 mg·L^-1Cd²⁺,4.53‰ at 0 mg·L^-1 Cd²⁺,and the pollution index (PI) was 3.06. The micro-nucleus ratio and PI decreased when the accompanied surfactant LAS was also presented or the pH values decreased to 4.5 or 3.5. In the meantime,many deformed nuclei and grains were observed in the root tip cells. The growth of the Vicia faba roots was restrained, and the root cells were not easy to be scattered. Therefore,the toxicity of Cd²⁺ was increased by its combination with surfactant or acid rain. The Cd²⁺ toxicity to Vicia faba cells at pH3.5 was stronger than that at pH4.5. When the mutation effect of contaminant with high concentration or with strong toxicity to plant cell was tested, the contaminant should be diluted for at least three times,and hence, the highest micro-nucleus ratio and pollution index (PI) could be found.