The invention provides a firing tool for a THz glass insulator. The firing tool comprises an upper positioning tool and a lower positioning tool, wherein a first hole, a second hole and a third hole are formed in the lower side of the upper positioning tool, the diameter of the first hole is 0.127 mm, the diameter of the second hole is 0.7 mm, and the diameter of the third hole is 1.1 mm; and a fourth hole, a fifth hole and a sixth hole are formed in the upper side of the lower positioning tool, the diameter of the fourth hole is equal to the diameter of the third hole, the diameter of the fifth hole is equal to the diameter of the second hole, the diameter of the sixth hole is equal to the diameter of the first hole, and all the holes are coaxial and vertical in an axial direction. A firing method for the THz glass insulator comprises the following steps: conducting heating at room temperature for 40 minutes until T1 is reached, preserving heat for 5 to 6 minutes, carrying out reheating for 20 minutes until T2 is reached, preserving heat for 9 to 10 minutes, carrying out reheating for 20 minutes until T3 is reached, preserving heat for 5 minutes, conducting cooling to T4, preserving heat for 5 to 6 minutes, conducting cooling to T5, preserving heat for 9 to 10 minutes, conducting cooling to room temperature, and taking out a final product. The tool is simple in structure, and the percent of pass of sintered products is high.