Supershort avalanche electron beam (SAEB) plays an important role in nanosecond-pulse discharges. this paper aims at reviewing experiments results on characteritics of SAEB and its spectra in different gases in nanosecond-pulse discharges. All the joint experiments were carried in the Institute of High Current Electronics of the Russian Academy of Sciences and the Institute of Electrical Engineering of the Chinese Academy of Sciences. In these experiments, the generation of a SAEB in SF6 in an inhomogeneous electric field was studied on three generators with pulse rise times of 0.3, 0.5 and ~2 ns. Firstly, the comparison of SAEB parameters in SF6 with those obtained in other gases (air, nitrogen, argon, and krypton) is introduced. Secondly, the SAEB spectra in SF6 and air at pressures of 10 kPa (75 torr), and 0.1 MPa (750 torr) are reviewed and discussed. Finally, 1.5-D theoretical simulation of the supershort pulse of the fast electron beam in a coaxial diode filled with SF6 at atmospheric pressure is described. the simulation was carried out in the framework of hybrid model for discharge and runaway electron kinetics. the above research progress can provide better understanding of the investigation into the mechanism of nanosecond-pulse discharges.