The invention relates to a deep-low-temperature gold-iron thermocouple with a temperature measuring ball, which is characterized in that a heat-conducting temperature measuring ball is clamped at a left opening of an axial through cavity, the left opening of the axial through cavity is a bell mouth which gradually contracts from the left end to the right end along the axial direction, the diameterof the end surface at the large-opening end of the bell mouth is equal to the diameter of the temperature measuring ball, the diameter of the end surface of the small-opening end of the bell mouth isless than the diameter of the temperature measuring ball, and the inner wall surface of the bell mouth is a conical surface; the left end of a thermocouple rod is sleeved by a pressing cover used forpressing the temperature measuring ball against the conical surface; the pressing cover is provided with a through hole, one end of the through hole is connected with the outside world, the other endof the through hole aligns to the temperature measuring ball, and the aperture of the through hole is less than the diameter of the temperature measuring ball; the axial through cavity is coaxially provided with a thermocouple wire in a penetrating manner, the left end of a low-temperature adhesive bar presses against the temperature measuring ball, and the right end of the low-temperature adhesive bar presses against a sealing plug; the left end of the thermocouple wire is connected with the temperature measuring ball; and the right end of the thermocouple wire runs through the sealing plugand a compacting cap and extends outward.