The utility model relates to the technical field of high-voltage electric power systems, and in particular relates to a 220kV porcelain outer sleeve metallic oxide lightning arrester for a high-altitude electric power system. The 220kV porcelain outer sleeve metallic oxide lightning arrester comprises a grading ring, two lightning arresting units, a metal gasket and an insulation base, wherein the two lightning arresting units are connected in series by the metal gasket; the top end of the lightning arresting unit at the upper part is connected with the grading ring, and the lower end of the lightning arresting unit at the lower part is fixedly connected with the base via the insulation base. According to the utility model, the structure of the 220kV porcelain outer sleeve metallic oxide lightning arrester for the high-altitude electric power system is redesigned; a reasonable internal resistor disc column and an electric conducting rod support structure are adopted, so that the potential distribution of a high-creep-distance MOA for a high-altitude area is effectively equalized, failure is prevented, and the safe and stable running of the high-altitude electric power system is ensured obviously.