Oat (Avena sativa L.) is receiving increasing appreciation as nutritious diet food due to its nutritional benefits and health-care function. Genomics study of oat will help identify and clone the genes underlying important agronomic traits, thus benefiting for the exploitation of oat germplasm resources. This article reviews the important progresses on oat genomics study from the following aspects: (1) the genome designation，genome size and ploidy level variations in the genus Avena; (2) the oat genetic linkage maps constructed by different types of molecular markers; (3) the sequencing of diploid and hexaploid oat species; (4) functional annotation of genes based on quantitative trait locus (QTL) and genome-wide association study (GWAS) approaches; and (5) population genomics or pan-genome study of oat. The prospects of genomics study in oat are proposed, in order to provide reference information for molecular breeding of oat in future.