Objective@#To observe the effects of perinatal exposure to benzo[a]pyrene (B[a]P) on the expression of pancreatic duodenal homeobox-1 (PDX-1) and mitochondrial transcription factor A (TFAM) and mitochondrial DNA copy number in offspring mice, and to explore the role of maternal exposure to B[a]P in the pancreatic function damage of offspring mice.@*Methods@#Forty pregnant rats were randomly divided into the control group, the lowest dose group (2 μg/kg), the low dose group (200 μg/kg), medium dose group (800 μg/kg) and high dose group (1 600 μg/kg), with 8 rats in each group. From day 1 of pregnancy, each exposed group was given 0.2 mL/100 g body weight of B[a]P and corn oil mixture by gavage once a day until 3 weeks after delivery, while the control group was given the same dose of corn oil. The pancreatic tissue of three-week-old mice were collected after abdominal anesthesia for insulin immunohistochemical detection. The protein and mRNA expression levels of PDX-1 and TFAM, as well as mitochondrial DNA copy number were detected. Spearman rank correlation analysis was used to analyze the correlation between B[a]P exposure dose and the above indicators.@*Results@#The insulin-positive area ratio and average optical density of insulin in the medium and the high dose groups were significantly lower than those in the control group (all P<0.05). The insulin-positive area ratio and average optical density of insulin were negatively correlated with the B[a]P dose (rs=-0.862 and -0.858, both P<0.05). The protein expression levels of PDX-1 and TFAM in the high dose group were significantly lower than those in the control group (both P<0.05). The protein expression levels of PDX-1 and TFAM were negatively correlated with the B[a]P dose (rs=-0.756 and -0.799, both P<0.05). The mRNA expression levels of PDX-1 and mitochondrial DNA copy number in the medium and high dose groups were significantly lower than those in the control group, and the mRNA expression level of TFAM in the high dose group was significantly lower than that in the control group (all P<0.05). The mRNA expression levels of PDX-1, TFAM, and mitochondrial DNA copy number were negatively correlated with the B[a]P dose (rs=-0.722, -0.550 and -0.840, all P<0.05).@*Conclusion@#Perinatal exposure to B[a]P can induce the damage of islet β cells in offspring rats, which may be related to the decreased expression of PDX-1 and TFAM and the copy number of mitochondrial DNA.