The invention relates to a ring electrode lightning arrester for a contact system of urban rail transit, which comprises an insulator and a high-voltage cross rod, wherein the high-voltage cross rod is connected with the high-voltage side of the insulator; the ring electrode lightning arrester is characterized by also comprising a lightning arrester body, a ring electrode component and an installing plate component, wherein the installing plate component is fixed on the high-voltage side cross rod; the lightning arrester body is installed on the installing plate component; the ring electrode component is fixed on the lightning arrester body; and an air gap is formed between the ring electrode component and the insulator. Because the series gap has an effect of isolating the working voltage of the contact system, the lightning arrester body nearly loads no system operation voltage under normal working conditions, and the lightning arrester withstands a voltage only when the lightning surge breaks down the gap, so that the problem that a valve plate of the lightning arrester is aged due to long-term loading of the working voltage is reduced, and the lightning arrester has the technical characteristics of long service life, high reliability and maintenance free. External insulation can install a composite jacket molded once in the known technology, and the lightning arrester has light weight and is convenient in installation.