Abstract: An olefin-based thermoplastic elastomer composition comprising a thermoplastic elastomer blended with other resins and rubbers is provided. The thermoplastic elastomer contains polypropylene resin and an olefin-based copolymer rubber, and optionally, a linear polyethylene resin, and the thermoplastic elastomer has been crosslinked to a gel content of 95% or higher. A polyolefin resin, an olefin-based copolymer rubber and a softening agent are further blended with optional inorganic filler to provide the olefin-based thermoplastic elastomer composition. This composition is excellent in oil resistance and extrudability, and well-adapted for use as an energy-saving, resources-saving elastomer in applications including surface or skin material in autoparts, industrial mechanical parts, electric and electronic parts, and construction materials.