Among the junction temperature monitoring methods of insulated gate bipolar transistor （IGBT），the temperature-sensitive parameter method has attracted wide attention because of its fast response speed，low cost and easy on-line detection. Previous studies have shown that the gate threshold voltage （ V_{TH}）among the temperature-sensitive parameters has good temperature properties，but it is easily affected by current oscillation by direct measure-ment. Therefore，an indirect calculation method of threshold voltage based on Miller platform under resistive load was proposed. Firstly，the switching transient process of IGBT under resistive load was described，and the theoretical basis of V_{TH} indirect calculation method was discussed. Then，the V_{TH} was calculated indirectly by the voltage value of Miller platform in the switching process. Finally，the effectiveness of the method was proved by experiments.