Large wide-area mesophase pitch (MP) could be prepared by thermal polymerization method from asphaltene (AP) extracted from coliquefaction residue. The influences of temperature, soaking time, and initial gauge pressure on MP formation were investigated. The results indicate that initial gauge pressure has a strong impact on MP formation except for temperature and time. Increasing initial gauge pressure appropriately promotes the coalescence and rearrangement of mesophase microspheres, but too high pressure hinders microspheres to coalesce. The optimum formation condition of large wide-area MP with lower softening point (similar to 270 degrees C) is determined by the temperature at about 400 degrees C, initial gauge pressure at about 1 MPa, and a soaking time of about 10 h. Based on SEM result, mesophase microspheres present a globe structure, they grow and coalesce obeying the mechanism of homogeneous nucleation.