The invention relates to a helicopter hoisting auxiliary device for an ultrahigh voltage cup tower head and a hoisting method. The hoisting auxiliary device comprises a crank arm support rod device, a flowerpot guide rail component and a limiting tray, wherein the crank arm support rod device comprises support rods, an adjusting screw rod and a ratchet wheel adjusting mechanism; the ratchet wheel adjusting mechanism can drive the adjusting screw rod to forward or backward rotate around self-axis and cause an upper support rod to be away from or close to a lower support rod; the flowerpot guide rail component comprises a first guide rail component, a second guide rail component and a third guide rail component; each guide rail component is equipped with a lateral panel used for guiding; the lateral panels are in different heights. According to the hoisting method, the helicopter hoisting auxiliary device is adopted for dividing the tower head into a plurality of hoisting components and hoisting in sequence; the hoisting components are assembled on ground in advance; the helicopter hoisting auxiliary device provided by the invention can solve the hoisting problem of all sections of tower materials of the ultrahigh voltage cup tower head; the construction efficiency is high; the safety is high; the damage to the environment is small.