The invention relates to the field of ship propulsion system design, and particularly discloses a two-stage longitudinal vibration isolation shafting which is provided with a propeller, a stern rear bearing, a stern light shell structure, a stern shaft, a stern front bearing, a pressure-resistant body structure, a stern shaft sealing device, a longitudinal vibration isolator, a vibration isolation thrust bearing, a middle shaft, a middle bearing, an elastic coupler, a propulsion motor and the like from the stern to the bow. By arranging the longitudinal vibration isolators and the vibration isolation thrust bearings, the whole shafting forms a two-stage longitudinal vibration isolation system, the mass ratio u of the two-stage vibration isolation system is designed to be 0.5-1, the mass ratio is increased as much as possible during design, the rigidity ratio is designed to be u + 1, and the shafting can have the better vibration isolation effect than a single-stage vibration isolation system at the middle-high frequency band except the second-order inherent frequency, and vibration noise generated by the ship tail propeller-shaft system is reduced.