Disclosed are methods for combining a thermoplastic polymer with a carbon nanomaterial. More particularly, A method of preparing a thermoplastic polymer combined with a carbon nanomaterial includes combining the carbon nanomaterial with a pyrene derivative by stirring 1 to 40 wt % of a carbon nanomaterial, 1 to 40 wt % of a polycyclic aromatic hydrocarbon derivative, and 20 to 98 wt % of a solvent with a mechanical mixer. According to the present invention, the resulting materials exhibit excellent tensile strength, tensile modulus, electromagnetic shielding effects and anti-static effects, and the like.