Barley is the fourth largest cereal crop in the world and rich in barley β-glucan, which has the function of lowering plasma cholesterol, controlling blood glucose, immune regulation and anti-oxidation. In the food system, barley β-glucan can act as a hydrophilic colloid. Previous studies have focused on the optimization of processing technology for adding barley β-glucan food, and its application as a functional food ingredient. The barley β-glucan can also affect the food processing process between the physical and chemical reactions, thereby affecting the food texture, nutrition and function. The distribution and purification of barley β-glucan in barley grains, the progress of analysis of the structure of barley β-glucan, and the structure-activity relationship between the microstructure of β-glucan and the structure of glucan gel were reviewed in this paper. It was found that the molecular weight of β-glucan and the ratio of the cellotriosyl and the cellotetraosyl were important factors affecting the gel formation process and the microstructure of the gel. The mechanism of barley β-glucan gel formation and its properties, as well as its effect on physical properties of food were also discussed. This paper provides reference to avoid negative impact of barley β-glucan on the products and exert its physiological function in food.