Objective: To study the effects of maternal chlorpyrifos(CPF)exposure on the expression of COX2,CREB and BDNF in offspring of mice. Methods: Female mice were randomly divided into control group,solvent group(cpf0 )and administration group. The administration group was divided into three subgroups according to the dosage,namely,cpf 0.3 group,cpf 0.6 group and cpf 1.2 group. After maternity,5 litters were selected from each group. The concentration of CPF in plasma of mother and offspring mice was determined by HPLC,and the expression of COX2,CREB and BDNF in hippocampus of offspring mice was measured by ?uorescence quantitative PCR and Western blot. Results: Compared with the control group and solvent group,CPF was detected in the plasma of mother and offspring mice after CPF exposure,and there was a dose relationship between the two groups(P<0.01). The expression of COX2 and protein in hippocampus of offspring mice P<0.05) increased,while the expression of CREB and BDNF decreased(P<0.01, . Conclusions: CPF can act on the hippocampus of offspring mice through placental barrier and lactation pathway, and activate COX2-CREB-BDNF pathway to produce toxic effects.