Objective To investigate the clinical characteristics of Parkinson disease（ PD） patients accompanied with cognitive impairment（ CI） and the sleeping status. Methods A total of 394 patients with PD in Beijing Tiantan Hospital from May 2014 to May 2017 were enrolled. According to CI level， the patients were divided into PD without cognitive impairment（ PD-NCI） group（ n=94，23.86%）， PD with mild cognitive impairment（ PD-MCI） group（ n=177，44.92%）， and PD with dementia（ PDD） group（ n=123，31.22%）. The demographic data of the patients were collected and the cognitive function of the patients was evaluated by Montreal Cognitive Assessment Scale（ MoCA）. The general cognitive function and the cognitive domains of the three groups were compared. Sleep status was assessed by video polysomnography（ v-PSG）. The correlation between the total score of MoCA scale， cognitive domain score and the results of v-PSG in patients with PD and CI was analyzed. Results There was no statistical significance in the differences in gender， age of onset， education level and duration of disease among the 3 groups（ P＞0.05）. The total score of MoCA scale in PD-NCI group， PD-MCI group and PDD group decreased one by one（ 22.20±4.99），（17.17± 4.36） and（ 10.73±4.85） （F=143.146，P ＜ 0.01）. The scores of MoCA scale in each cognitive field were significantly decreased in turn （P＜ 0.01）. Compared with PD-NCI group， PD-MCI group had less total sleep time， lower sleep efficiency and increased arousal frequency（ P＜0.05）. Compared with PD-MCI group， PDD group had less total sleep time， lower sleep efficiency and increased arousal frequency（ P＜ 0.05）. The sleep efficiency of PD-CI patients was positively correlated with the total score of MoCA scale， visual spatial function， executive function， delayed recall and attention score（ P＜ 0.05）. The number of arousal in PD-CI patients was negatively correlated with the total score of MoCA scale， delayed recall and attention score（ P＜0.05）. Conclusions The incidence of CI was higher in PD patients. The overall cognitive function and cognitive fields of PD patients with CI were significantly impaired. The total sleep time decreased， the sleep efficiency decreased， and the number of awakenings increased， which was related to the impairment of the overall cognitive function and some cognitive fields.