The invention discloses a folding propeller device. The folding propeller device comprises a base assembly, a steering shaft, a steering arm, a steering cylinder, a boom cylinder, a transmission assembly, a cage assembly, a propeller assembly, a transmission shaft, hinge pins, a bolt and a control system. The base assembly is internally provided with plane bearings, and a mounting hole and a rotating arm are arranged in the base assembly. The lower end of the steering shaft is integrally connected with the transmission assembly, and the steering arm is assembled at the upper end of the steering shaft in an orderly mode. The telescopic end of the steering cylinder is connected with the steering arm, and the telescopic end of the boom cylinder is connected with the rotating arm. The spheralcage assembly is fixedly installed on an input shaft of the transmission assembly, and the propeller assembly is fixedly installed on an output shaft of the transmission assembly. The folding propeller device is scientific in design, compact in structure, reliable in performance, convenient to assemble and disassemble and low in cost, the folding propeller device is mounted on a rear bottom plateof a vehicle in a folding mode, and can provide ideal power and reliable steering for the vehicle to float across the water surface.