We report the new synthetic way to fabricate nanometer-sized conducting polymer particles in large quantities using seeded polymerization. This approach represents an alternative route to produce conducting polymer nanoparticles in large quantities while the previous methods such as microemulsion polymerization, vapor deposition polymerization and dispersion polymerization didn't. Especially, Poly(3,4-ethylenedioxythiophene) was employed as the shell material owing to its high stability in the air and the excellent electrical properties. The prepared PEDOT nanoparticles were applied to the conductive nanofillers in the matrix in order to cast conductive thin films. The conductivity changes of the composite films with different nanofiller contents were investigated and nanofiller behaviors were monitored using FE-SEM.