The invention discloses an LED junction temperature or average LED array junction temperature measuring method. A formula is established for the LED junction temperature, the effect of the self-heating process of an LED light source generated by a low current on the junction temperature is small, the thermal resistance between a thermostat and the LED light source is small, and the temperature of the thermostat replaces the LED junction temperature. Centroid wavelengths under different thermostat temperatures are measured, and the relational expression between the centroid wavelengths and the junction temperature is established. The junction temperature of an LED under the work condition can be conveniently worked out according to the formula and the centroid wavelengths of the LED light source under the measuring working conditions. According to the method, single-time calibration and multi-time measurement are achieved. Operation is easy, and the steps of the measuring method are similar to the steps of a peak wavelength method and a blue and white comparing method. Only a conventional optical and electrical test device is needed. The repeatability of the measurement on the centroid wavelengths is high, and the centroid wavelengths are used for representing that the junction temperature error is small. An LED pin is not in contact. The method can be used for measuring the junction temperature of a single LED and can be used for measuring the average junction temperature of an array composed of a plurality of LEDs, and the application range is wide.