The invention relates to a composite modified conductive engineering plastic of carbon nanotubes or nano-ZnO and conductive carbon powder and a preparation method thereof. The engineering plastic comprises the following components by weight percent: 0.5%-5% of nanoscale conductive material, 5%-25% of micro-scale conductive carbon powder and the balance plastic. In the method of the invention, conductive carbon powder is dispersed in the resin monomer to be polymerized, then polymerization is initiated to obtain conductive carbon powder/resin master batch; by adopting the in-situ dispersion polymerization technology, conductive carbon powder is easier to disperse in the micromolecular organic monomer and polymerization is initiated on the basis of good dispersion to obtain the composite macromolecular material which is filled with conductive carbon powder and has good distribution performance. The prepared conductive carbon powder/resin master batch can be conveniently mixed with plastic.