The invention discloses an automatic spiral lock for a carriage door. The automatic spiral lock comprises a bothway hydraulic oil cylinder, an oil cylinder connecting rod, an oil cylinder hinged base, a guide base, a lock plate, a profiling sliding sleeve, a profiling sliding pillar, an oil cylinder connecting pin shaft and an oil cylinder hinged pin shaft. A hydraulic rod in the bothway hydraulic oil cylinder is matched with the inner diameter of the oil cylinder connecting rod and connected with the oil cylinder connecting pin shaft. The external diameter of one end of the oil cylinder connecting rod is in movable fit with the guide base. The external diameter of one end of the oil cylinder connecting rod is in movable fit with the internal diameter of the profiling sliding sleeve. The lock plate is connected between the guide base on the oil cylinder connecting rod and the profiling sliding sleeve. The oil cylinder connecting rod is connected with the profiling sliding pillar, and the profiling sliding pillar is matched with a sliding channel in the profiling sliding sleeve. The oil cylinder hinged base and the profiling sliding sleeve are connected with a bottom side band of a carriage. The oil cylinder hinged base is hinged to a hinged lug on the bothway hydraulic oil cylinder through the oil cylinder hinged pin shaft. The automatic spiral lock for the carriage door has the beneficial effects that the structure is simple and reasonable, the carriage door can be opened or locked conveniently, the phenomenon that a driver needs to open and close the carriage door when leaving a cab is avoided, and labor intensity is relieved.