Objective To investigate the effect of triptolide(TP) on expression of C1q in the hippocampus of model rats with Alzheimer’s disease(AD). Methods Thirty male SD rats were randomly divided into control group, AD model group and TPtreated group.Each group had 10 rats. The AD model group was established with bilateral microinjection of aggregated beta-amyloid protein(Aβ)SUB>1-40/SUB> into hippocampus in rats and Morris water maze test was used to judge that the model was successful or not. The control group was established with bilateral microinjection of normal saline into hippocampus in rats.The TPreated group rats were administered TP ［0.4mg/(kg.d)］ intraperitoneally after the AD model was made successfully.The change of expression of C1q protein and mRNA were observed with immunohistochemical staining and RT-PCR 15 days later. Results Immunohistochemically, the cell number of C1q positive staining in hippocampus of the AD model group（67.89±9.22） increased obviously as compared with the control group（36.27±5.09）（EM>P/EM>0.01）, and their average optical density（0.2918±0.0347） increased obviously as compared with the control group（0.1980±0.0183）（EM>P/EM>0.01）, the average optical density of C1q positive