The invention provides a portable very-fast transient high-frequency electric field measurement system. The measurement system comprises a signal sensing device, a first transmission optical fiber, and a signal processing device. In the signal sensing device, an electric field signal antenna receives a very-fast transient high-frequency electric field signal released by a GIS switch, the very-fasttransient high-frequency electric field signal is modulated as an optical signal after the signal conditioning is performed on the received signal through the antenna signal receiving circuit. In thesignal processing device, a first photoelectric conversion circuit converts the optical signal into the electric signal; the sampling circuit samples the electric signal, the signal processor is usedfor processing and storing the sampling data. Through the hardware optimization, the measurement system can satisfy a measurement requirement on the GIS transformer substation high-frequency transient electric field. By adopting optical signal transmission, the interference and attenuation in the transmission process are avoided, and the measurement accuracy is provided, thereby providing supportfor evaluating the electromagnetic compatibility of the GIS transformer substation.