This paper analyzes the similarities and differences of testing principles and structures between a calibration furnace of high temperature thermocouples and a tungsten tube furnace, focusing on researching the indexing method. Through the indexing experiments by B, PtRh40-PtRh20, Ir40Rh-Ir, and tungsten rhenium thermocouples and other high-temperature thermocouples in high temperature distinction, the correction value data of the system derived experimentally are listed and analyzed within the temperature range of 1500~2300 ℃ . The experimental results prove good reproducibility of the high temperature thermocouple calibration furnace. It can be used to calibrate all kinds of high temperature thermocouples within the temperature range of 1500~2300 ℃ in oxidizing and reducing atmosphere.