To observe the effect of electroacupuncture (EA) of "Xiusanzhen" ［bilateral "Yingxiang"(LI20)+"Yintang"(GV24 )］ on synaptophysin (SYN), postsynaptic density protein-95 (PSD-95), Iba-1 CD68 microglia and complement C related protein expression of hippocampus in Parkinson's disease dementia (PDD) mice, so as to explore its mechanism in improving memory impairment of PDD. Male C57BL/6 mice were randomly divided into control, sham operation, model and EA groups, with 10 mice in each group. The PDD model was established by injecting 6-OHDA into the medial forebrain tract. EA (2 Hz, 1 mA) was applied to unilateral LI20 and GV29 for 20 min once daily for consecutive 14 days. Morris water maze and new object recognition test were used to evaluate the learning and memory ability. Western blot was used to detect the expression of SYN and PSD-95 proteins in hippocampus. Immunofluorescence was used to label Iba-1 CD68 microglia and C1q positive cells in hippocampal CA1 region. The content of C3 protein in hippocampus was