In this paper, we investigate the relativistic magnetic reconnection in collisionless plasmas with the 3-dimensional particle-in-cell simulations. The work is motivated by the fact that an explanation of the narrow energy spectrum of gamma-ray flash observed in Crab Nebula is still not clear in astrophysics. The results on the mono-energetic electron bunch generation obtained in our work support the idea on the ultra-relativistic electron acceleration via the reconnection of the magnetic field lines. Our results contribute to research on the relativistic regimes of fast magnetic field dissipation, where the large-scale magnetic field energy is converted to the energy of collimated charged particle beams. It also provides a basis for the future experiments to connect the laser facilities with the astrophysical phenomenon.
