Objective：To investigate the central analgesic mechanism of using moxibustion of Guanyuan point to treat patients with primary dysmenorrhea through collecting the blood oxygenation level-dependent（BOLD） signal by restingstate functional magnetic resonance imaging（rsfMRI） technology and analyzing the brain functional change of patients with primary dysmenorrhea before and after moxibustion of Guanyuan point by amplitude of low frequency fluctuation（ALFF） method. Methods：RsfMRI scanning was per－formed on 20 primary dysmenorrhea patients before the treatment（moxibustion of Guanyuan point） and at 5 min after the treatment. All data were analyzed by ALFF. Paired t-test was used to process the data and to compare the ALFF value before and after the treat－ment. BOLD signal changes after moxibustion on Guanyuan point were observed from the view of brain metabolic activity. Results：ALFF values of the right cingulate gyrus，left insula，left precuneus，right postcentral gyrus，left uncus，left superior temporal gyrus，middle temporal gyrus，left precentral gyrus，left middle frontal gyrus，right inferior frontal gyrus were increased significantly after moxibustion（P<0.05，after correction），while the ALFF values of the left occipital lobe，right superior frontal gyrus，left medial frontal gyrus，left middle frontal gyrus，right posterior lobe of cerebellum and right superior temporal gyrus were decreased（P<0.05，after cor－rection）. Conclusions：RsfMRI technology and ALFF method can be used to study the activity changes of brain after moxibustion of Guanyuan point. The treatment of moxibustion of Guanyuan point may arouse the functional changes of a series of pain-related brain regions，which may provide imaging evidence for the study of the mechanism of central analgesic by moxibustion of Guanyuan point.