The invention relates to a flexible DC land cable double layer sheath which is characterized by comprising cable water-resistant conductors, a conductor shielding layer, an insulating layer, an insulating shielding layer, a water-resistant buffer layer, a metal sheath, an internal layer waterproof external sheath and an external layer flame-retardant external sheath. Multiple cable water-resistant conductors are externally provided with the conductor shielding layer. The external side of the conductor shielding layer is provided with the insulating layer, the insulating shielding layer, the water-resistant buffer layer and the metal sheath which are arranged from inside to outside in turn. The external part of the metal sheath is provided with the internal layer waterproof external sheath which is also externally provided with the external layer flame-retardant external sheath. A double layer sheath structure is formed by the internal layer waterproof external sheath and the external layer flame-retardant external sheath. The flexible DC land cable double layer sheath is safe and reliable in operation and can meet the related specifications and requirements so that the flexible DC land cable double layer sheath can be widely applied to cable application occasions of humid environment and high flame retardation requirement.