Abstract: A MTT-based semiautomated colorimetric assay and leaf dipping method were used to study the effects of chlorpyrifos, carbosulfan and abamectin on silkworm ovarian cell and the larva respectively. The results showed that the effects of insecticides on silkworm cell were not always the same as that of the larva. And the difference of toxicity between chlorpyrifos and carbosulfan was distinct in significance level. The toxicity of the technical and the emulsifiable concentrate of chlorpyrifos to silkworm ovarian cell was significantly different by MTT-based semiautomated colorimetric assay. It was suggested that live insect-based assay cannot entirely be replace by cell-based assay, and the technical is suitable for cell-based assay. Key Words: insecticides; silkworm; cell; MTT method; toxicity