The present invention discloses a multifunctional ultrafast electron gun of a transmission electron microscopy. The ultrafast electron gun of a transmission electron microscope comprises: a laser source, an electron gun body and a laser introducing module. The electron gun body comprises: an electron gun sleeve comprising a first section sleeve and a second section sleeve; and, a cathode, an acceleration electrode and an anode arranged in up-down order, wherein the cathode and the acceleration electrode are located within the first section sleeve and the anode is located within the second section sleeve. The laser introducing module includes an introducing module sleeve sealedly connected between the first section sleeve and the second section sleeve and provided with a laser incoming window in a side thereof; and a laser reflective mirror located in the introducing module sleeve, which is configured to face right the laser incoming window and configured adjacent to a central axis of the introducing module sleeve, and the reflective face of which is configured to make an angle of 45° with the central axis of the introducing module sleeve. The multifunctional ultrafast electron gun of a transmission electron microscopy according to the present invention achieve the best coherence performance of the electrons obtained in the case of the photoelectron emission compared with those in the prior art.