The utility model relates to a flexible direct current land cable duplex sheath, its characterized in that: it includes cable block water conductor, conductor shield, insulating layer, insulation screen, the buffer layer that blocks water, metallic sheath, the waterproof oversheath of inlayer and outer fire -retardant oversheath, it is a plurality of the cable blocks water the conductor and is provided with outward conductor shield the conductor shield outside from interior to exterior set gradually insulating layer, insulation screen, buffer layer and metallic sheath block water, the metallic sheath outside is provided with the waterproof oversheath of inlayer is located the waterproof oversheath of inlayer still is provided with outward outer fire -retardant oversheath, waterproof oversheath of inlayer and outer fire -retardant oversheath constitute double -deck sheath structure. The utility model discloses operation safe and reliable can satisfy the relevant requirement of standardizing, can the wide application use the place in the moist and fire -retardant cable that expects much of environment.