Objective To explore the relationship of protein kinase B1 ( PKB1 ) gene polymorphisms in PI3-K pathway of BDNF and event-related potentials in depression.Methods The design of case-control research was used ,and 91 major depressive patients and 65 normal controls who were made in age and gender matched with patients were measured auditory event-related potential P300 and contingent negative variation ( CNV ) in the day when two groups were collected.Polymerase chain reaction (PCR) and direct DNA sequencing technology were used to detect PKB1 gene polymorphisms.Three SNPs that named rs3001371 ,rs2494738 ,rs1130214 were selected from 3 representative BLOCK Districts of PKB1.Two independent samples t test was used to analysis P300 and CNV between two groups,and the same way to analysis the average level of P300 and CNV and PKB1 SNP genolatency of P2(P＜0.05) and lower amplitude of P3a(P＜0.01 ) ,P3b(P＜0.01 ) and P3 (P＜0.01 ) ;CNV had der had statistical difference (P＜ 0.05 )in PKB1 rs3001371 gene between C/C and C/T genotype combined which included C allele, and T/T genotype.The amplitude of P3a( (5.93 ± 2.35 ) μV, P3b(6.51 ± 3.00) μV, P3 (6.27±2.43) μV) were lower than TT Genotype ( (7.45 ±2.19)μV, (8.63 ±3.57)μV,(8.04 ±2.57)μV,respectively).The mean of CNV indicators were not found different in statistics among the rs3001371 genotypes.Conclusions PKB1 gene rs3001371 polymorphism is associated with the principal component of P300 amplitude in patients with Major depressive disorder which suggest that genetic factors may have a certain impact on cognitive function in the patients with Major depressive disorder.