The invention provides a wood-grain-imitated co-extruded plastic-wood profile. The wood-grain-imitated co-extruded plastic-wood profile comprises a surface layer and a base material, wherein the adding amounts of plastic and a functional aid in the surface layer are more than the adding amounts of the plastic and the functional aid in the base material, so that the cost is favorable to be reduced; the surface layer is subjected to color adjustment by virtue of a main color and a secondary color (a third color can be increased according to requirements), so that the effects of the color shade and the layer variability of the surface layer can be well achieved. The invention further provides a preparation method of the wood-grain-imitated co-extruded plastic-wood profile. The preparation method comprises the processes of granulation, synchronous extrusion and surface treatment. According to the preparation method, surface layer particles including main color particles and secondary color particles are respectively granulated and are uniformly mixed for co-extruding the surface layer, and the surface layer is subjected to surface treatment in a 'hot plate and cold roller' manner. The co-extruded plastic-wood profile prepared by virtue of the preparation method is low in cost, excellent in water resistance, corrosion resistance and aging resistance and durable, further has the grains, color gradation and texture of imitated and natural wood, so that the user experience is improved.