The invention discloses an in-situ combustion discardable inner spiral ignition device. The device comprises a lengthwise extending sleeve, a heat insulation pipe arranged in the sleeve, an oil pipe arranged in the heat insulation pipe, and a combustor arranged at the lower end of the oil pipe, wherein the sleeve is provided with a tail end used for extending into the ignition device and an initial end used for extending out of a well; the sleeve and the heat insulation pipe form a first annual space; the heat insulation pipe and the oil pipe form a second annual space; a packer used for fixing the heat insulation pipe and isolating heat is arranged in the first annual space. According to the device, the problem of recovery of the combustor does not need to be considered, the fuel combustion time of the thickened oil reservoir combustor is prolonged, and further the ignition efficiency and the fireflooding effect are improved.