The present disclosure relates to a polyolefin-natural fiber composite composition for extrusion molding, and more particularly to a polyolefin-natural fiber composite composition, which comprises polyolefin resin, natural fiber, thermoplastic elastic rubber and an anhydrous maleic acid-grafted polypropylene-based compatibilizer, and is useful as a material for an extrusion molded article by obtaining an effect of improving dimensional stability, mechanical properties and surface quality through adjusting three-dimensional structure and particle size of the polypropylene-based compatibilizer and binding rate of the maleic acid.