Abstract: The study is devoted to the method development concerning the measurement of a light-emitting diode crystal temperature based on the method of direct stresses. An automated experimental device is described to perform crystal temperature measurements among working LEDs. The results of indirect measurements are presented for heating and cooling dynamics of crystals at various currents. They presented the analysis of thermal processes occurring in a crystal during its heating by a flowing current. It was confirmed experimentally and theoretically that the developed method of a light-emitting diode crystal measurement can be used to evaluate the heating of a light-emitting diode crystal under real operating conditions during the design of light devices.