The invention discloses a hoisting method for a main shaft of a large bulb tubular unit and a hoisting auxiliary device. Through setting up a supporting and walking mechanism in a cabin of a water turbine and by utilizing the way of combining upper hoisting with lower supporting, the hoisting method and the hoisting auxiliary device are particularly applicable to the condition that the hoisting weight of a main shaft of a large bulb tubular water turbine is heavy; the stress of a bearing trolley is supported by adopting a double-rail track in a hoisting process; the main shaft is jointly supported by a reliable shaft jacking device and the bearing trolley when a crane hook is dismantled for the first time; the axial plug-in mounting and movement are carried out by dragging the bearing trolley; the state of the main shaft is stable in the whole hoisting process; the safety of a hoisting scheme is good; the operability is high; moreover, the main hoisting work is reflected in the mounting and the disassembly of a track truss; the track truss is mounted and disassembled without using a plant crane; a longer mounting line construction period can be saved, and the project progress is ensured.