The present invention provides an underwater traffic tunnel. The device comprises a body immersed in water, a connector, and a ventilation system. The body comprises a first cavity for providing a passage space and a second cavity located below the first cavity. The second cavity is in communication with water; the connector connects the body and the water bottom and is used to resist buoyancy, and the ventilation system is in communication with the first cavity and extends above the water surface; the body of the present invention is safely immersed in water, and a vessel can navigate freely above the body; the second cavity is in communication with water and is not easy to be overturned by seawater; the connector resists buoyancy; the ventilation system can prevent damage by external forces through deformation and movement, and an escape system can be activated in emergency situations, which is more safe and reduces the impact of changes in the earth crust on the tunnel.