The present invention provides a method for monitoring electrical power in high-speed rail traction power supply networks/systems, comprising: collecting voltage and current analog signals from a traction power supply system, and converting the voltage and current analog signals into voltage and current digital signals; obtaining, by a processing unit, digital signals and transfer commands; compressing, by the processing unit, the digital signals according to the transfer commands to digital signal frames; and constructing a data link between the processing unit and a storage unit and transmitting the compressed digital signal frame to the storage unit. The processing unit may use run-length coding algorithm to compress the digital signal to be stored to obtain several compressed digital signal frames. Under different conditions of data link, transmission of compressed digital signal frames is adjustable to improve the reliability of digital signal transmission.