The invention relates to a light-control power source switch of a testing system under high-temperature environments. The switch comprises a photoelectric diode, a filter, an I/V (current-to-voltage) converting and amplifying device, a voltage control switch and a power source, wherein the photoelectric diode is connected with the filter, the filter is connected with the I/V converting and amplifying device, the I/V converting and amplifying device consists of an I/V converter and a logarithm converter and is connected with the voltage control switch, one of two ends of the voltage control switch is connected with the power source, the other end of the voltage control switch is connected with the power source input end of a testing device, and the power source is used for providing a working power source for the testing device. The light-control power source switch has the advantages that the switch is a light-control device which is used for controlling the opening and closing of the power source switch by the photoelectric diode, and is suitable for controlling the automatic opening and closing of the testing device which is not suitable for manual operation occasions; the sunlight interference is avoided in the circuit design, the light wave generated by triggering the light source is absorbed by the photoelectric diode, is amplified by photoelectric conversion and is shaped and filtered, and then the effect of closing the power source switch by the voltage control switch is realized.