Based on the pot experiments in sand culture, both the removal of pollutant Cadmium by Kandelia candel and the toxicity of Cadmium to seedlings Kandelia candel were determined in the absence and presence of Methamidophos, respectively. The results showed that, although 100 mg·L^-1 Methamidophos had no effect on the removal of pollutant Cadmium by soil-culture Kandelia candel, there was a synergistic toxicity effect between Cadmium and 100 mg·L^-1 Methamidophos to seedlings Kandelia cande. It assumed that this synergistic toxicity effect might result from the membrane-lipid pemxidation of Cadmium vs. seedlings Kandelia candel: this peroxication would no doubt enhance the ability of Kandelia candel to be penetrated, then facilitate the transfer of Methamidophos from water into Kandelia candel, thus lead to the synergistic toxicity between Cadmium and Methamidophos. Therefore, it is suggested that the mixture toxicity between Cadmium and other pollutants should be considered to determine the tolerance concentration of Cadmium to Kandelia candel.