The utility model discloses a self-adaption flexible ground well casing protective device which comprises a flexible pipe, a first pipe connector fixed to one end of the flexible pipe, a second pipe connector fixed to the other end of the flexible pipe and a tensile component connected between the first pipe connector and the second pipe connector. The tensile component can be disconnected to be free of the restraint on the first pipe connector and the second pipe connector. Part of pipe section of the self-adaption flexible ground well casing protective is the flexible pipe capable of extending and being bent, the two ends of the flexible pipe are connected together through the tensile component capable of being disconnected, assembling requirements can be met, meanwhile, the tensile component can be disconnected when bearing the certain-strength comprehensive acting force of drawing, shearing and extrusion, then the flexible pipe generates corresponding deformation according to force bearing conditions rather than being disconnected and damaged, a gas diversion pipeline is kept not to be damaged, gas leakage or pipeline blocking can be avoided, and the fact that gas extraction work is carried out smoothly is guaranteed.