The invention relates to an auxiliary device of electric transmission line live-working, and specifically to a hoisting device for large-tonnage live wire, comprising a hoisting cross arm, a leveling stand, a reinforcing device and a hoisting device, wherein there are two leveling stands which are respectively located at both sides of the hoisting cross arm, the upper leveling stand is fixed on the angel steel of iron tower cross arm, and the upside is under fixed connection with hoisting cross arm; the reinforcing device is arranged at the middle part of hoisting cross arm and between the two leveling stands, the upside and downside thereof are respectively under fixed connection with hoisting cross arm and steel angle of iron tower cross arm; hoisting device is arranged at both ends of hoisting cross arm in symmetry, each end is arranged with two hoisting devices. The hoisting device achieves large-tonnage live wire hoisting with smaller insulating materials by adopting four-point hoisting structure, and has fall-arrest backup protection for wire hoisting, which guarantees safety and reliability of large-tonnage wire hoisting live-working.