ObjectiveTo discuss the relationship between objective sleep quality and cognitive function in remission depression patients with insomnia. MethodsA total of 47 patients with depression in remission in Beijing Huilongguan Hospital were enrolled. Insomnia Severity Index （ISI） and the sleep efficiency calculated by the first four items of Pittsburgh Sleep Quality Index （PSQI） were defined as insomnia. Among the selected patients， 22 subjects were classified into insomnia group， and 25 subjects in non-insomnia group. The objective sleep status of all subjects was evaluated by polysomnography （PSG）， and the cognitive function was evaluated with the Repeatable Battery for Assessment of Neuropsychological Status （RBANS）. A regression model was established to explore the relationship between objective sleep quality and cognitive function in remission depression patients with insomnia. ResultsThere was statistically significant difference in immediate memory factor scores of RBANS between depression patients in remission with and without insomnia （t=-2.102， P<0.05）. The sleep efficiency （Z=-2.113， P<0.05）， the proportion of N3 sleep stage （Z=-3.175， P<0.01） and the duration of N3 sleep stage （Z=-3.196， P<0.01） in insomnia group were all lower than those in non-insomnia group， and the nocturnal awakening （Z=-2.058， P<0.01）， the proportion of N1 sleep stage （Z=-2.399， P<0.05） and the duration of N1 sleep stage （Z=-2.463， P<0.05） were higher than those of the insomnia group. Within insomnia group， the increased proportion of REM sleep was correlated with the improvement of attention function （β=0.953， 95% CI： 0.123~2.038， P<0.05）， and the increase of nocturnal awakening was correlated with the decline of delayed memory （β=-0.173， 95% CI： -0.325~-0.024， P<0.05）. ConclusionObjective sleep is associated with cognitive impairment in remission depression patients with insomnia， the proportion of REM sleep has a positive impact on attention function， and frequent nocturnal awakening at night has a negative impact on delayed memory.