The present invention relates to an extruded expanded thermoplastic polyurethane elastomer bead and a preparation method therefor. The bead consists of components of the following parts by weight: 100 parts by weight of a thermoplastic polyurethane elastomer, 0.01-0.5 parts of a foaming nucleating agent, and 0.01-0.2 parts by weight of an antioxidant. The preparation method comprises: mixing materials, then putting the mixture into an extruder for granulation to produce a particle raw material suitable for foaming, finally, putting the particle into a foam extruder, and die foaming then underwater pelletizing, thus obtaining a product bead. The present invention utilizes an extrusion method to prepare expanded thermoplastic polyurethane beads. Control of the working conditions of the foaming process could lead to acquiring an expanded=bead of a controllable density, the cell density evenly distribute. The overall production process is easy to operate. Without any special limit or requirement placed on the equipment, this method is suitable for industrial continuous production.