The main voltage heating equipment in UHV substations consists of 1000 kV CVTs, 1000 kV GIS outlet bushings, and 1000 kV arresters. They exhibit small differences in surface temperature and are easily exposed to environmental factors. Precise infrared temperature measurements are typically performed to diagnose defects under ideal environmental conditions. However, if the onsite environmental conditions cannot meet the requirements in a short time, further defects may occur. Therefore, it is necessary to study a correction method for temperature measurement results under non-ideal environmental conditions. In this study, three types of UHV heating equipment temperature field simulation models were established and combined with the theory of heat transfer to study the influence of environmental factors such as light intensity, temperature, and wind speed on the surface temperature difference of UHV heating equipment. The results revealed that the enhancement of these three factors decreased to varying degrees the surface temperatures that needed to be corrected to the true temperature difference under ideal environmental conditions. Finally, data fitting was used to obtain a curve expressing the measured and real temperature differences, and the correction method of the surface temperature difference of the UHV heating equipment under non-ideal environmental conditions. The accuracy of the correction results was verified through the field application of a substation.