Abstract: Apopulation of earthworm Eisenia foetida was exposed to single and binary-combined contamination of phaeozem by methamidophos, acetochlor and Cu. The result showed that one of three test chemicals had its toxicity on the earthworm population,and the single toxic sequence of the chemicals was acetochlor > methamidophos > Cu.The values of their LD₅₀ were 0.307, 0.708 and 118.70 mg穔g^-1, respectively. The difference was depended on the biological mechanisms of the earthworm population.Acetochlor and Cu in soil could be absorbed by the earthworm population through penetrating through the skin of an earthworm.The result also showed that Cu could swell the toxicity of methamidophos,whether it was in low or high concentration by the binary-combined toxic effect test.Cu in low concentration could decrease the toxicity of acetochlor, but in high concentration,Cu could increase the acetochlor toxicity in soil. Therefore,these three pollutants were dangerous to the ecological security of soil ecosystem and soil-health quality. Furthermore, when the chemicals in same soil environment act one another, they could boost up the potential danger of soil ecosystem contaminated by the three pollutants.The joint toxic effects of various chemicals were in relation to their different concentration combinations in soil.