In recent years, marine resources become strategic resources and attract widespread attention due to their unique physiological and physiochemical properties. Alginate, a prominent marine polysaccharide, is derived from the cell walls of brown algae and certain bacteria. Alginate oligosaccharides (AOS) are degradation products of alginate with smaller molecular weight, improved water solubility, and lower viscosity. AOS exhibits distinct biological activities, such as anti-microbial, anti-tumor, anti-oxidant, anti-inflammatory, anti-diabetic, and prebiotic properties, showing great potential in planting, breeding, food, material, and medicine fields. The bioproduction of AOS using Alginate lyase (Alyase) has emerged as a prominent trend in AOS production. This review provides the recent advances in the structure, physiological functions, applications, and production of AOS. It particularly delves into the bioproduction of AOS catalyzed by Alyases, discussing enzyme classification, enzymatic properties, crystal structure, catalytic mechanism, molecular modification, immobilization, high-efficiency expression, and utilizing low-cost biomass as feedstock. Additionally, the review concludes by proposing prospects for further development of AOS.