MXene is an intriguing new class of 2D transition metal carbide and/or carbonitride, which can be obtained by etching the active metal element in the MAX with the help of hydrofluoric acid, lithium fluoride with hydrochloric acid or inorganic fluoride. MXene has high specific surface area, high conductivity, excellent optical, electrical, and mechanical properties. After introducing MXene, the coating can obtain the properties of photothermal conversion, conductivity, reinforcement, flame retardant and antibacterial to broaden their application in the fields of sensors, special protection, and so on. Firstly, this paper reviews the preparation methods of MXene, including hydrofluoric acid etching, modified acid etching, molten fluoride etching and fluorine-free etching. Meanwhile, the influence of exfoliation on MXene is discussed. Then, three modification methods which can improve the surface reactivity, electrical and stability of MXene are introduced in detail, namely intercalation modification, doping modification and antioxidation modification. In addition, their applications in sensors, electromagnetic shielding, photothermal and other functional coatings are summarized. Finally, the future re-search direction and development prospect on the functional application of MXene are prospected.