A composite High Intensity Discharge (“HID”) arc tube includes a discharge tube and two outwardly extending tubes. The discharge tube is a composite two-layer shell with an outer of fused quartz glass or Vycor quartz glass, and a layer of translucent polycrystalline alumina (“PCA”). The outwardly extending tubes are made of fused quartz glass or Vycor quartz glass, and a layer of polycrystalline alumina is applied at ends of the outwardly extending tubes close to an arc chamber. After the arc tube is sintered at a high temperature, the electrode is sealed by being separated into two segments. The first segment of the outward extending tube applied with PCA is sealed by glass solders, and the second segment of quartz glass is sealed by a molybdenum foil under pressure.