Objective To observe the effects of acupuncture on the behaviors and the expressions of Fis1 and OPA1, as well as mitochondrial ultrastructure in the hippocampus of mice with Alzheimer disease (AD); To explore the mechanism of action of acupuncture for AD.Methods Forty male SAMP8 mice were randomly divided into acupuncture group and model group, with 20 mice in each group. Another 20 male natural aging mice with the same age (SAMR1 mice) were set as the normal group. Acupuncture group chose Shenshu, Baihui, Xuehai and Geshu for intervention. 8 weeks later, Morris water maze was used to test the mice behaviors, and then hippocampus organization was taken. Western blot was used to detect the expressions of Fis1 and OPA1 and mitochondrial ultrastructure in hippocampal neurons of mice was observed by transmission electron microscopy.Results Compared with the model group, the escape latency of acupuncture group was significantly shortened (P<0.05), and the stay time in the former platform quadrant and former platform crossing times were significantly increased (P<0.05). The expression of Fis1 in the hippocampus of acupuncture group decreased significantly (P<0.05), while the expression of OPA1 increased significantly (P<0.05). The mitochondrial ultrastructure in hippocampus in the acupuncture group was effectively improved, and the mitochondrial surface density and body density were both increased in the acupuncture group compared with the model group (P<0.05).Conclusion Acupuncture may play a potential therapeutic role in AD by decreasing the expression of Fis1, increasing the expression of OPA1, recovering the injury of mitochondrial ultrastructure.