【Abstract】Objective To explore the attention bias of depressive patients toward negative emotional faces and the lateralization effect of brain on emotional information processing. Methods 31 subjects in depression group (MDD) and 28 subjects in healthy control group (HC) were tested by dot-probe task. Event-related potentials (ERP) were recorded during the experiment. Results By the analysis of N170 induced by negative emotional faces and neutral emotional faces, MDD and HC groups showed no attention bias to negative stimuli. The amplitude of N170 produced at the O1 region of the brain at the MDD group was significantly smaller than that in the O2 region; this cerebral lateralization was not observed in the HC group. Compared with HC group and MDD group, the N170 amplitude of MDD group was significantly smaller than that of HC group at the O1 region, and there was no significant difference in N170 amplitude between the two groups at the O2 region. Conclusion When facial stimulation is processed, the cognitive abilities of the left and right brains of depressive patients are different, which results in great amplitude difference of EEG signals, and provides more valuable reference indexes for clinical diagnosis in the future.