The present invention relates to a preparing method of a polyolefin resin mono chip including: forming a thermoplastic resin composite by impregnating a fiber reinforcing agent having a length of 5 mm to 20 mm into a molten mixture including a propylene homopolymer of which a molecular weight distribution Is 3 to 6, and a colorant, wherein a cooling speed at room temperature of the thermoplastic resin composite is 19° C./min or more. In addition, the present invention relates to a polyolefin resin mono chip including: a thermoplastic resin composite including a polymer substrate including a propylene homopolymer of which a molecular weight distribution is 3 to 6, and a colorant; and a fiber reinforcing agent having a length of 5 mm to 20 mm and impregnated into the polymer substrate, wherein an impact strength measured according to ASTM D256 is 200 J/m or more.