Abstract: Objective To investigate the characteristics of memory impairment in patients with chronic insomnia. Methods Chronic insomnia patients （chronic insomnia group） admitted to our hospital and healthy subjects （control group） receiving physical examination were selected to evaluate the sleep quality by using Pittsburgh Sleep Quality Index （PSQI） and the objective insomnia by polysomnography （PSG）. The cognitive function was measured by Montreal Cognitive Assessment （MoCA）. The memory function was assessed by nine-box maze test. The test results were statistically compared between two groups. The correlation between sleep parameters and memory function was analyzed. Results The total sleep time, sleep latency, sleep efficiency and sleep-wake cycle significantly differed between the chronic insomnia and control groups （all P < 0.05）. Compared with the control group, the proportion of N1 was significantly increased, the proportion of N3 was remarkably decreased and the proportion of rapid eye movement （REM） was considerably decreased in the chronic insomnia group （all P < 0.05）. The number of errors of object working memory and spatial working memory in the chronic insomnia group was significantly larger than that in the control group （both P<0.05）. Correlation analysis demonstrated that sleep efficiency and the proportion of REM were negatively correlated with the working memory, whereas the proportion of N2 was positively correlated with the working memory （all P < 0.05）. Conclusions Chronic insomnia patients have deteriorated spatial working memory and object working memory, probably correlated with the changes of the proportion of slow wave sleep and the decrease in the proportion of REM.