By adding naphthalene-based mesophase pitch (NBMP) into refined coal tar pitch (RCTP), pyrolysis products were obtained by dry-blending and co-carbonization method. The properties of pyrolysis products were characterized by polarizing microscope, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometer (XRD) and Raman spectroscopy. The result shows the NBMP can obviously change the mesophase development of RCTP because it can promote the formation of mesophase spheres during the pyrolysis process. The carbon yield and aromaticity of pyrolysis products were increased with the increase of NBMP content. The anisotropic texture was wide-area structure when the NBMP content was 5 wt%. However, when the content of the additive is increased to 10 wt%, pyrolysis products will appear coking. The main role of this additive is to accelerate the reaction rate as the "nucleating agent" of the thermal condensation reaction.