Abstract: Objective To investigate the protection effect and mechanism of PhaseⅡenzyme inducer CPDT (5,6-dihydrocyclopenta[C]- 1, 2-dithiole-3-thione) against threo-hydroxyaspartate-induced injury of motor neuron in the cultured spinal cord slices of rats. Methods Organotypic spinal cord slices of rat pup was divided into normal control group, model group(THA 100μmol/L) and PhaseⅡenzyme inducer CPDT(5, 15, 30μmol/ L) treated groups. The morphology change of spinal cord slices was observed with inverted microscope. Ventralαmotor neurons' survivals were evaluated by immunohistochemical staining with monoclonal antibody SMI32, a nonphosphorylated neurofilament marker. Lactate dehydrogenase (LDH) and malonaldehyde (MDA) levels in culture medium were also measured. Results The slices of THA group showed that the number of Ventralαmotor neurons significantly decreased, but LDH enzyme activity and MDA level in culture medium increased. After CPDT(15, 30μmol/L) pretreatment, the spinal cord slices in vitro grew well and showed the similar change with the slices of normal control group. The number ofαmotor neurons significantly increased with intervention of CPDT, compared with model group. LDH and MDA level in culture medium also decreased. Conclusion PhaseⅡenzyme inducer, CPDT may inhibit THA-induced motor neuron injury by inhibiting lipid superoxide and scavenging free radical.