The present invention provides a fully vulcanized thermoplastic elastomer comprising a rubber phase with a controllable particle size and a spheroidic shape, the preparation and use thereof. Fully vulcanized powdery rubber is blended with plastic by conventional method for blending rubbers, and thus obtaining a fully vulcanized thermoplastic elastomer, which comprises a rubber phase with a controllable particle size and a spheroidic shape, and which shows high tensile strength and high elongation at break, good appearance and good processibility.