The internal-Mg-diffusion (IMD) processed MgB₂ wires obtain high transport critical current densities (J_c) at varied temperatures and magnetic fields. However, liquid Mg just partially reacted with B particle in these strands because the formed compact MgB₂ layer inhibited the further infiltration of liquid Mg. Consequently, the IMD wires tend to have a small superconducting area fraction. In this paper, 15 mol% Mg particle was added into B powder to improve the fraction of superconducting area for IMD wires. The best non-barrier J_c of 3 x 10⁴ A/cm² and the best J_e of 9.7 x 10³ A/cm² were attained at 4.2 K and 10 T by the Mg particle-added IMD wire processed by 650 ^oC and 4 h. Optical microscopy (OM) was used to identify different phases in the wires.