The utility model relates to a dead-lock-proof butt connection device of a closed cavity. The device comprises a dead-lock-proof swivel nut arranged in a front casing section and an inclined bolt penetrating into a back casing section to be fixed in the dead-lock-proof swivel nut and further comprises a sealing cover covering the portion of the dead-lock-proof swivel nut exposed to the outside of the front casing section and fixed with the front casing section. A plurality of self-rotating-proof protruding blocks are arranged in the sealing sleeve. An annular first boss and an annular second boss are arranged on the dead-lock-proof swivel nut along the circumferential direction of the sleeve wall. The first boss is matched with the front casing section, and a self-rotating-proof groove is arranged on the second boss corresponding to the self-rotating-proof protruding blocks. The butt connection device meets the requirements for sealing and connection locking of parts of an aircraft, is simple and quick in product assembly operation, has good practicability, simultaneously has low requirements for structure size, is not sensitive to locking torque and has good process feasibility.