the present disclosure relates to a polymer nanocomposite including a metal - carbon nanotube coated glass fiber and graphite , in which a metal - carbon nanotube coated glass fiber serving as an electromagnetic wave shielding material is hybridized with graphite having an excellent heat conductivity , thereby improving the electromagnetic wave shielding performance in a low frequency range . the polymer nancomposite according to the disclosure is broadly applicable to a variety of fields requiring electromagnetic wave shielding performance such as , for example , various electronic component housings for a vehicle , components of an electric vehicle , a mobile phone , and a display device , and a method of preparing the polymer nanocomposite .