The invention discloses a gamma-ray electronic spectrometer comprising the following parts of a flight duct having an entrance port and an exit port, wherein a conversion body is arranged inside; a deflection electromagnet located at the exit port of the flight duct and used for receiving the space electron flow formed after the conversion body is radiated by gamma-ray; at least one electron beamcurrent detector for receiving the space electron flow after the deflection action of the deflection electromagnet and converting the same into an electric signal; and an oscilloscope connected to anelectron beam current detector through the cable A and used for receiving the electrical signal. By using the method of a deflection magnetic field combined with signal conversion, the gamma-ray electronic spectrometer can achieve fast measurement of the gamma-ray energy spectrum, has good accuracy and reliability, is more suitable for pulsed gamma-ray measurement especially after the introductionof a synchronous machine, and further improves the stability and safety of operation together.