Objective To explore the cognitive function of the patients with bipolar depression (BP), unipolar depression (UP) and their first-degree relatives.Methods 52 patients with BP and 49 their first-degree relatives ,67 patients with UP and 59 their fi~t-degree relatives, 97 normal controls were tested by information, arithmetic, digital symbol, digital span test, block design,logical memory (included immediately and delayed) , visual memory(included immediately and delayed), Stroop Test (included Stroop C and Stroop CW), trail making test (included Part A and Part B) ,verbal fluency and modified Wisconsin card sorting test(M-WCST).Results The scores of digital symbol, block design, immediately logical memory, delayed logical memory, immediately visual memory,delayed visual memory,trail making test B and WCST in the patients with BP and UP were worse than those in normal control(P＜0.01).The score of WCST in the patients with BP was lower than that in the patients with UP ((3.02± 1.96), (4.40± 1.13), P＜0.01).The score of WCST in the relatives of the patients with bipolar depression was worse than that in the normal control((4.32±1.66), (5.15±1.27), P＜ 0.05).Conclusion The patterns of impaired cognitive function on sustained attention,concept of visual space,visual memory,verbal memory and executive function are similar in the patients with BP and UP.The executive function of the patients with BP is worse than the patients with UP.