Oats are rich in soluble dietary fiber, particularly β-glucans. β-glucan is a water-soluble polysaccharide primarily found in the endosperm, subendosperm, and germ of cereals, which is linked by β-D-glucopyranosyl units through β-1,4 and β-1,3 glycosidic bonds. Due to its unique structural properties, it has health benefits such as antioxidant and intestinal protective effects. Oat β-glucans is not only applied in dairy products and baked goods, but also receives widespread attention in aquatic products. This paper summarizes the extraction processes of oat β-glucan, discuss in detail the impacts of extraction rates and purification effects of various processes. Meanwhile, the review provides an overview of the research progress on the applications of oat β-glucan in aquatic products, encompassing the application status of both aquaculture and various aquatic products. Furthermore, this paper explores the problems encountered in current research and applications of oat β-glucan, in order to offer theoretical reference for the further development and utilization of oat β-glucan.