The utility model discloses a temperature monitoring device for high voltage electrical equipment. The temperature monitoring device comprises a temperature detecting unit, a signal conversion unit and a coding output unit, wherein the coding output unit comprises a CPLD chip and an optical fiber sending circuit; the temperature detecting unit converts the temperature values of monitoring points to resistance signals and transmits the resistance signals to the signal conversion unit, and the signal conversion unit converts corresponding resistance signals to frequency signals and transmits the frequency signals to the CPLD chip; the CPLD chip adopts a coding way and transmits a temperature coding signal to an external control system through the optical fiber sending circuit in an optical signal way, and the external control system completes reading of the temperature coding signal in a decoding way. The influence of high voltage on temperature measurement is isolated, while the temperature monitoring device has the advantages of further simplifying the structure, improving reliability, improving precision, increasing transmission distance and reducing cost.