〔Abstract〕 Objective To explore the effect of interferon regulatory factor IRF9 gene silencing on apoptosis of cerulein induced exocrine pancreas AR42 J cells and elucidate the role of IRF9 gene in the development of acute pancreatitis. Methods The AR42 J cells at logarithmic growth stage were divided into blank control group, negative control group and IRF9 silencing group. After successful transfection of siRNA, the model of acute pancreatitisin vitrowas constructed by cerulean treatment. The mRNA and protein expression levels of IRF9 gene, Caspase 3 and Caspase 9 in AR42 J cells were detected by qRT-PCR and Western blot. The apoptosis rate of AR42 J cells in each group was detected by Annexin V-FITC/PI double staining assay. Results ① The mRNA and protein levels of IRF9 gene in each group increased after cerulean treated 24 hours, and the mRNA and protein levels of Caspase 3 and Caspase 9 also significantly increased, indicating that the expression levels of IRF9 and apoptosis-related genes were up-regulated when acute pancreatitis occurred.② Compared with the blank control group, the apoptosis rate of AR42 J cells in IRF9 silencing group significantly reduced after cerulean treatment(P<0.05). Conclusions The expression levels of IRF9, Caspase 3 and Caspase 9 were up-regulated and the apoptosis rate increased when acute pancreatitis occured. The silencing of IRF9 gene reduced the apoptosis of cerulean induced acute pancreatitisin vitro.