PURPOSE. To analyze the altered amplitude of low-frequency fluctuation (ALFF) of the brain using resting-state functional magnetic resonance imaging (fMRI) in patients with primary open-angle glaucoma (POAG). METHODS. Resting-state fMRI was conducted in 21 POAG patients and 22 age-matched healthy control subjects. After the ALFF and fractional amplitude of low-frequency fluctuation (fALFF) for slow 4 and slow 5 bands were calculated, the results between POAG patients and healthy controls were compared. Then the correlations between ALFF/fALFF values and the disease stage of POAG were analyzed. RESULTS. Compared with controls, POAG patients showed significantly decreased ALFF/fALFF values in the visual cortices, posterior regions of the default-mode network (DMN), and motor and sensory cortices. Meanwhile, ALFF/fALFF values in the prefrontal cortex, left superior temporal gyrus (STG), right middle cingulate cortex (MCC), and left inferior parietal lobule (IPL) significantly increased in POAG patients. Hodapp-Anderson-Parrish (HAP) score for POAG was positively correlated with ALFF values of the right superior frontal gyrus (SFG) and negatively correlated with that of the left cuneus. For the slow 5 band, the fALFF values of the bilateral middle temporal gyri (MTG) of POAG patients were negatively correlated with HAP score. CONCLUSIONS. Primary open-angle glaucoma is a neurodegenerative disease involving multiple brain regions, including the visual cortices, DMN, limbic system, and motor and sensory networks. Moreover, the alterations in some of these networks are correlated with the progression of POAG; for the abnormal spontaneous neural activities in the left cuneus, bilateral MTG and right prefrontal cortex are correlated with glaucoma severity.