A helicon wave plasma (HWP) discharge with strong magnetic field was investigated. The HWP was produced with an internal Nagoya III antenna that is perpendicular to the magnetic field and driven by a 13.56 MHz radio-frequency (RF) source. HWP was characterized in terms of electron density, electron temperature and plasma potential using a single Langmuir probe in Ar gas. The result of Langmuir probe shows that the electron density increases with RF power, but saturate above 700 W at a density of 2×1019 m-3. Scanning electron microscopy (SEM) was extensively used to characterize the quality of the graphite surface. The result of SEM shows the surface of graphite that exposed to plasma processing has exhibited smoother and compacter surface topography. Meanwhile, the concentration of impurity on the graphite surface decreases with plasma processing.