Scenedesmus obliquus growth inhibition test was carried out to assess the toxicity of soil contaminated by heavy metals. The results showed that the growth rate of Scenedesmus obliquus was positively related to the concentration of heavy metals added to soil, and it was decreased with the increasing concentration of heavy metals. Two parameters were chosen and the sensitivities were compared. It was found that the cell growth rate was more sensitive than OD growth rate. The orders of general detection limit by EC50 of different metals were Pb > Cu > Zn > Cd by using cell growth rate as the test index and Pb > Cu > Cd > Zn by using OD as the test index. This study also indicated that under the complex pollution condition, the toxicity of heavy metals in soil was stronger than that in the case of soil contaminated by single metal.