Objective To examine the effects of Triptolide (T10) on the Aβ deposition and senile plaques formation in the hippocampus by using the APP/PS1 double transgenic mice model of AD (APP/PS1dtg). Methods Eighteen Male APP/PS1dtg mice aged at 45 months were used in this study. The mice were divided into 3 groups randomly, High-5μg/(kgI>&#/I>8226;d) T10 (T10 H,EM>n/EM>=6), Low-1μg/g(kgI>&#/I>8226;d) T10 (T10 L,EM>n/EM>=6) and placebo (PLC,EM>n/EM>=6). Intraperitoneal administration of T10 and capacity solvents (PLC group) was given in a period of a total of 45days. After 45days of treatment, the mice were sacrificed and the brains removed for processing. The brains were separated along the middle sagittal sulcus. The left side was used for the histological study staining 6E10 immunohistochemical and Congo red methods, and quantitative analysis by unbiased stereological counting. The right hippocampus was dissected, Western blotting was performed to assess the change of protein level for Aβ. Results Compared with the PLC group, the total area of 6E10 positive Aβ plaques in the hippocampus of T10 H was reduced by 35% (P<0.001), and that of T10 L reduced by 18% (P<0.05); and the total area of SP in the hippocampus of T10 H group was reduced by 32% (P<0.001), and in the T10 L reduced by 27% (EM>P/EM><0.05). Western blotting protein analysis also displayed that T10 H group Aβ protein levels in the hippocampus was lowest, Aβ protein levels in PLC group