The invention provides an ultra-fast electronic diffraction system based on an X-waveband photocathode microwave electron gun, belonging to the technical field of ultra-fast electronic diffraction; the ultra-fast electronic diffraction system is characterized in that the X-waveband photocathode microwave electron gun replaces a DC high-voltage photocathode microwave electron gun in the existing Kev ultra-fast electronic diffraction system and is used as an electron source; and correspondingly, an X-waveband pulse microwave power unit is adopted and high-quality electron beams ranging from 0.5MeV to 1.5MeV is easily obtained, thus leading the electron number in each electron beam bunch to be improved to 2 to 3 magnitude and correspondingly saving a plurality of samples and testing time of the diffraction samples to be researched, thereby leading the obtaining of single diffraction sample spot to be possible.