In order to meet the special requirements of EMCCD, an EMCCD power supply was designed based on optocouplers characteristics.The isolation of the input and control signals was realized by use of the photoelectric isolation characteristic of the optocoupler.The continuous adjustment of the output voltage was achieved by working in the active region of optocouplers receiving transistor.The power-on initial state was controlled by using the saturation and cutoff characteristics of the optocouplers receiving triode.The high-speed optical receiving diode and totem pole circuit were used to achieve the synchronous control of the DC-DC power.The temperature characteristics of optocoupler circuit were analyzed, and feedback circuits were added to reduce the temperature effects.Experiment results show that:1) the EMCCD power supply designed based on optocoupler can meet the application requirements;and 2) the temperature caused change rate of output voltage is 8.9% of the one before improvement.