Objective To assess the characteristic of normal tension glaucoma (NTG) patients with mild cogni?tive impairment (MCI). Methods This study included twenty-six cases of normal tension glaucoma patients who were diagnosed at ophthalmology department of Peking University Third Hospital. All the participants were examined by us?ing the scales of Montreal Cognitive Assessment (MoCA), mini-mental state examination(MMSE), clinical dementia rat?ing (CDR), activities of daily living (ADL), Hamilton anxiety scale (HAMA), Hamilton depression scale (HAMD), Pitts?burgh Sleep Quality Index (PSQI) and polysomnography (PSG). The patients were then divided into Group with MCI (16 cases) and Group without MCI (19 cases). Results There was no difference between the two groups in gender, age, edu?cation, depression, anxiety and body mass index (BMI) (P>0.05), but significant difference in MoCA scores (P<0.05). The incidence rate of sleep disorder of PSQI in was 28.6%(10/35 patients) of total NTG patients, 43.8%(7/16 patients) in Group with MCI, and 15.8% (3/19 patients) in Group without MCI, respectively. The PSQI score was higher in Group with MCI than in Group without MCI (P<0.05). Sleep efficiency was higher in Group without MCI than in Group with MCI (P<0.05), but no difference was found between the two groups in six other indexes of PSQI (P>0.05). The in?cidence rate of sleep structure disorder of PSG in all the NTG patients was 85.7%(30/35 patients), 87.5%(14/16 pa?tients) in Group with MCI, and 84.2%(16/19 patients) in Group without MCI. Sleep time of NREM-N3 was significant?ly shorter in Group with MCI than in Group without MCI (P<0.05), but no difference was found between those groups in total sleep time, sleep efficiency, sleep latency and REM time (P>0.05). Conclusion NTG patients with mild cogni?tive impairment are more prone to sleep disorders, especially sleep structure disturbance and short NREM-N3 time may affect cognitive function.