Auxin response factors (ARF) are important transcription factors that can regulate the expression of auxin genes and influence the plant growth. ARFs regulate the transcription of auxin-responsive genes through binding to their promoters. In this study, a total of 24 ARF genes are identified and analyzed and named SiARF. A comprehensive overview of the SiARFs is undertaken, including phylogenetic analysis, the gene structures, chromosome locations, conserved motifs of proteins and gene expression.Twenty-four setaria italica ARF genes are distributed in all setaria italica chromosomes except chromosome. Setaria italica ARF proteins share one B3 DNA binding domain, which consists of threeαhelixes and sevenβsheets. And some of these proteins have a Aux/IAA domain and ARF domain. In addition, setaria italica ARF proteins are compared with the proteins in other species in order to discover the evolution of ARF genes. Our results also show that the expression of SiARF genes is diverse in different tissues.