Currently, numerous monoelemental two-dimensional (2D) materials, called Xenes, have been discovered, including graphyne (GD), silicene, germanene, arsenene, and borophene. Their structures, fabrication methods, as well as properties have been extensively explored. Based on their single-element composition, high optical response capability, excellent electrical-optical properties, large specific surface area (SSA) and easy modification, Xenes have been widely used in photoelectric applications (detection, modulation, light processing) and biomedicine (biological sensing, drug loading, bioimaging, etc.). Especially in the field of biomedicine, Xenes are expected to induce a great breakthrough. In this review, we introduce the structural characteristics, synthesis and modification methods of several common Xenes respectively. The general properties including optical, electronic, physical and chemical properties of Xenes are summarized. Their diverse utilization as biosensors for nucleic acid sequencing, bioactive detection, and cancer diagnosis, etc. are also explicitly explored. Finally, the challenges and future perspectives of Xenes in biosensor are discussed.