Conducting core-shell poly(styrene/pyrrole) (poly(St/Py)) particles were Successfully prepared by a one-step Solution route in soap-free emulsion polymerization. Hydrogen Peroxide (H2O2) and a truce of ferric chloride (FeCl3) were used as ail initiator couple to carry out Fe3+-catalyzed oxidative polymerization. The average particle size of the particle was approximately 250 nm and its core-shell morphology (shell thickness similar to 20-30 nm) was proved with transmission electron microscopy. The SEM images after CHCl3 dissolution supported a clear evidence of distinct core-shell morphology, and which was confirmed by DSC and TGA analyses. We proposed it growth mechanism for the formation of the core-shell poly(St/Py) particles based oil the time-evolution morphology of the particle. The result was also corroborated by the time-evolution GPC, FT-IR and zeta-potential data. The surface compositions of the particles were examined by X-ray photoelectron spectroscopy (XPS). The doped particles showed a high conductivity in the dry state.