Object To study the mechanism of triptolide solid lipid nanoparticle (TP-SLN) for decreasing liver toxicity of triptolide (TP). Methods With ig three doses of TP-SLN to mice for 60 d, the A LT, AST activities in serum and superoxide dismutase (SOD), glutathione peroxida se (GSH-Px) activites and malondialdehyde (MDA) contents in liver were determin ed. Results The activities of ALT, AST, SOD, GSH-Px and conten t of MDA between experimental group and blank group did not have remarkable diff e rence. However, the activites of ALT, AST, SOD, GSH-Px for the middle- (20 ?g /kg) and high-dose (30 ?g/kg) group were higher and the contents of MDA were lower than the experimental group. Conclusion TP-SLN can decrease the liver toxicity of TP.