Infrared temperature measurement technology is a common equipment fault detection method in power industry， which has important application in GIS equipment fault diagnosis. To improve the accuracy of temperature measurement，an infrared temperature measurement model is established and an SF6 transmittance correction method is proposed. First，an infrared temperature measurement model is established based on the thermal radiation theory，and its simplified model under different conditions is presented. Then，considering that the SF6 transmittance will influence the model output，and the correction method of SF6 transmittance under different conditions is presented to improve the temperature measurement accuracy. Finally，some experiments are carried out to verify the effectiveness of the established infrared temperature measurement model and the proposed SF6 transmittance correction method. The experimental results show that，compared with the method without SF6 transmittance correction，the temperature measurement accuracy is improved after using the proposed method，and the error is reduced by up to 66.7%. The proposed method lays the foundation for power grid fault detection and monitoring，and has broad application prospects in power grid fault detection and security operations.