Abstract: Various piping and cables are laid crisscross under the ground of cities and often adjacent to or intersected with underground pipelines, in addition, the soil around pipelines is very complicated, which results in large macro cell corrosion. Present corrosion protection method for urban buried pipeline is commonly adopting external corrosion protection combined with cathodic protection. According to the design of ca-thodic protection over Beijing City in Shanjing Gas Pipeline, discussions are made on such design difficulties as judging standard of cathodic protection, protective mode of sacrificial anode and a new technology of flexible anode impressed current cathodic protection, and theoretical analysis is performed based on the principle of corrosion electrochemistry and makes reasonable conclusions and puts forward relevant proposals.