A high-precision thermocouple provided by the present invention comprises a junction box, a first thermocouple, a second thermocouple and a third thermocouple. The first thermocouple comprises a first protection tube, a first casing pipe, a first conductor, a second conductor, a first binding post and a second binding post, the second thermocouple comprises a second protection tube, a second casing pipe, a third conductor, a fourth conductor, a third binding post and a fourth binding post, the third thermocouple comprises a third protection tube, a third casing pipe, a fifth conductor, a sixth conductor, a fifth binding post and a sixth binding post, and the first, second and third protection tubes have different lengths. According to the present invention, the temperatures of different temperature measurement points in a same temperature measurement space can be measured, and the lengths of the first, second and third thermocouples all can be adjusted, so that the high-precision thermocouple is adaptive to different temperature measurement places, and is simple in structure, accurate in temperature measurement and diverse in function.