Objective:To investigate the effects of single intermittent theta-burst stimulation on functional connectivity in patients with mild cognitive impairment(MCI).Methods:From July to November 2020, forty MCI patients were selected and randomly divided into iTBS true stimulation group and iTBS sham-stimulation group, with 20 patients in each group.iTBS targeted the left dorsolateral prefrontal cortex (DLPFC). Montreal cognitive assessment (MoCA), mini-mental state examination (MMSE), activity of daily living scale(ADL), Hamilton depression scale (HAMD) and Hamilton anxiety scale (HAMA) were evaluated at baseline.The resting state electroencephalography (rsEEG) was collected for 5 minutes before and after iTBS in the two groups.The phase lag index(PLI) of EEG functional connectivity was calculated, and the functional connectivity matrix diagram was drawn.SPSS 26.0 software was used for statistical analysis.Data were statistically analyzed by χ2 test, Wilcoxon rank sum test and independent sample t-test. Results:There were no significant differences in scores of MoCA, ADL, HAMD and HAMA between the two groups(all P>0.05). In the iTBS true stimulation group, compared with that before iTBS treatment(0.140(0.133, 0.144)), the PLI of β band increased significantly after iTBS treatment(0.146(0.136, 0.167))( P<0.05). The region of increased PLI was mainly concentrated in the central region(C3/C4-T7/T8). Compared with that before iTBS treatment(0.251(0.232, 0.299)), the PLI of α band increased after iTBS treatment(0.286(0.241, 0.359)), but the difference was not statistically significant( P>0.05). Conclusion:Single iTBS treatment can significantly increase the EEG functional connectivity in patients with MCI, indicating that iTBS targeting the left DLPFC can effectively regulate the EEG functional connectivity in patients with MCI, which may reveal the mechanism of iTBS in improving cognitive function in patients with MCI.