Background: Functional brain networks detected in resting-state functional magnetic resonance imaging (fMRI) have a small-world architecture that reflects a robust functional organization of the brain. Recent research has shown that this functional organization is disrupted in Alzheimer’s disease (AD). However, changes in the topological organization in amnesic mild cognitive impairment (aMCI) remain largely unknown. This study, using graph theoretical approaches, aimed to compare the topological properties of functional brain networks between healthy elderly and aMCI. Methods: Nineteen aMCI patients and 14 healthy elderly were enrolled in this study. All subjects were administered a comprehensive neuropsychological test. Functional data were acquired using a gradient-echo echo-planar pulse sequence sensitive to blood oxygenation level-dependent (BOLD) contrast. After several preprocessing steps to correct for intra-volume time delay and inter-volume displacement, as well as spatial normalization and temporal bandpass filtering (0.01 0.01 Hz), we calculated functional connectivity matrices for each participant by estimating interregional Pearson correlation coefficients among90 regions. Then a thresholding procedurewas implemented to convert these correlationmatrices into binarized brain networks. The resultant networks were further quantified by graph-based network metrics, including global attributes of clustering coefficient, characteristic path length and local nodal measures of degree, efficiency and betweenness. Results: We found that both aMCI patients and controls showed a smallworld topology, suggesting an optimal balance between functionally segregated and integrative organization. However, the global attributes such as characteristic path lengths and clustering coefficient showed no significant differences between the aMCI group and the control group. Furthermore, when comparing individual brain regions, the nodal degree, betweenness and efficiency of the right precentral gyrus (PreCG), superior frontal gyrus (SFGdor) and inferior frontal gyrus (IFGtriang) was significantly lower in aMCI patients’ networks than that of control group, implying dysfunctional connectivity, reduced network role and importance in these areas. Moreover, we also found that aMCI patients demonstrated significant increases in nodal degree and efficiency in left inferior orbitofrontal cortex (ORBinf) and parahippocampal gyrus (PHG).Conclusions:Although the large-scale functional brain system was not obviously disruptive in aMCI, several dysfunctional brain regions were detected. The findings suggest that the functional impairment and compensation may coexist in aMCI.