The invention discloses an adaptive protocol conversion system for high-voltage direct-current measurement and a using method thereof, and belongs to the technical field of power communication and automation. The adaptive protocol conversion system comprises a photoelectric conversion module, a protocol conversion unit and a communication interface module. The adaptive protocol conversion system can receive optical digital signals of various IEC60044-8 communication protocols such as standard FT3 and state grid FT3 data frame formats specified by IEC60044-8, and convert the optical digital signals into IEC61850-9-1, IEC61850-9-2LE and state grid IEC61850-9-2 network digital message signals meeting the IEC61850-9 standard in a high-speed, stable and real-time manner for optical digital protection, control, metering, measurement and test equipment. The protocol conversion system has the functions of intelligently identifying the Baud rate, the sampling rate, the link layer length and thenumber of check bytes of an input signal, has high-speed, stable and real-time conversion performance, and is widely applied to testing and verification of intelligent substations, converter stationmeasurement systems and digital equipment.