Abstract: Objective To investigate the changes in behaviors and brain structural network in patients with idiopathic rapid eye movement sleep behavior disorder (iRBD). Methods Twenty patients with iRBD (iRBD group) and 22 healthy control subjects were evaluated using the Unified Parkinson’s Disease Rating Scale (UPDRS) and Hoehn-Yahr staging. Diffusion tensor imaging and graph- theoretical analysis were performed for analyzing the topological characteristics of brain structural networks of the patients, and the correlation between the behavioral changes and the changes in the topological characteristics of the brain networks was analyzed. Results The UPDRS score was significantly higher in iRBD group than in the healthy control group (P<0.05). No significant difference was found in small-world attributes between the patients with iRBD and the control subjects (P>0.05). The patients with iRBD exhibited significantly shortened characteristic shortest path length Lp (P<0.05) and significantly increased global efficiency, local efficiency and assortativity (P<0.05). Examination of regional topological properties of the brain network revealed abnormal node properties in the frontal, temporal, parietal, occipital, and striatal and limbic lobes in patients with iRBD. The patients also had significantly increased degree centrality of the left pallidum and enhanced nodal efficiency in the left thalamus, superior temporal gyrus, temporal pole and bilateral superior occipital gyrus, bilateral putamens as well as the right gyrus rectus, amygdala, supramarginal gyrus, and middle temporal gyrus. The nodal local efficiency was significantly increased in the left superior frontal gyrus, middle cingulate gyrus, superior parietal gyrus, bilateral fusiform gyrus, right superior motor area, postcentral gyrus and angular gyrus of the patients with iRBD. The nodal shortest path was significantly shortened in the left superior motor area, pallidum, thalamus, superior temporal gyrus, temporal pole, bilateral putamens, bilateral superior occipital gyrus, right rectus gyrus, amygdala, supramarginal gyrus and middle temporal gyrus, and the nodal clustering coefficient was significantly lowered in the left superior occipital gyrus of the patients. In patients with iRBD, the UPDRS I score was positively correlated with the nodal efficiency in the right supramarginal gyrus (r=0.50, P<0.05) and local nodal efficiency in the right fusiform gyrus (r=0.53, P<0.05), and negatively correlated with the nodal clustering coefficient in the left superior occipital gyrus (r=-0.552, P<0.05). Conclusion Patients with iRBD present with abnormal changes in mental condition, behaviors, emotions, activities of daily living and motor functions. The brain structural network of patient with iRBD still has a small-world property with abnormal global topological property and abnormal distribution of local topological property in the cortex, striatum and limbic system.