Boron, like its neighboring elemental carbon, forms sp² hybrids, which tends to form complex polyhedral structures. Borophene is a two-dimensional allotrope of boron, and researchers have a strong interest in its structural and physicochemical properties. Since the preparation of borophene is very difficult, the study in this field has stayed on theoretical exploration for a long time. Recently, the boron monolayers has been successfully grown on Cu and Ag foils, and its atomic structure and photoelectric properties have also been systematically studied. These experimental studies have laid a good foundation for developing high-performance boron?based nanodevices. The theoretical research progress of borophene is firstly introduced. The preparation and properties of two-dimensional boron are described. Finally, the current research progress of two-dimensional boron thin film is summarized.