A contact network power supply cable connecting structure of an urban mass transit engineering can effectively improve the operation safety of the urban mass transit engineering, and comprises a contact network and an Internet cable tapping device; the two ends of large-section direct-current Internet cables with shielding layers are respectively connected with an Internet isolating switch and a busbar of the Internet cable tapping device; the two ends of small-section Internet cables or bare copper soft connecting wires are respectively connected with the busbar of the Internet cable tapping device and the contact network. The Internet cable tapping device is fixedly mounted on a tunnel wall very close to the contact network or a contact network upright post.