Inner surface coating for tubular samples was realized by the grid enhanced plasmasource ion implantation (GEPSII) method. In the GEPSII system, two electrodes, a central rodelectrode and a coaxial grid electrode were coaxially assembled inside the tube. Plasma wasgenerated between the electrodes by a radio-frequency (RF) oscillating power source. Plasmathen diffused through the grid and realized inner surface ion implantation by a negative highvoltage applied to the tube. The plasma was then divided, by the grid, into two regions, namelythe source plasma region and the diffused plasma region. The plasma’s self-bias between two RFpower source electrodes was measured. At the same time, the electron temperature and plasmadensity in the GEPSII system were measured by a scattering spectrometer. Results showed thatthe plasma properties of the two regions were entirely different; the plasma self-bias, which mightgreatly affect the sputtering rate of the central titanium electrode, depended on the electrodestructure, gas pressure and RF power. Inner surface coating for tubular samples was realized by the grid enhanced plasmasource ion implantation (GEPSII) method. In the GEPSII system, two electrodes, a central rodelectrode and a coaxial grid electrode were coaxially assembled inside the tube. radio-frequency (RF) oscillating power source. Plasmathen diffused through the grid and realized inner surface ion implantation by a negative highvoltage applied to the tube. the plasma was then divided, by the grid, into two regions, The plasma’s self-bias between the two RF power source electrodes was measured. At the same time, the electron temperature and plasmadensity in the GEPSII system were measured by a scattering spectrometer. ; the plasma self-bias, which might dramatically affect the sputtering rate of the central titanium electrode, depended o n the electrodetructure, gas pressure and RF power.