摘要： At present, the search for new methods of generation electromagnetic radiation in the terahertz frequency range (THz) has emerged as one of the most promising rapidly in science and engineering, developing areas of research including security and medical diagnostics. One of the modern solutions of the problem is the generation of electromagnetic (EM) waves due to the interaction of high-current relativistic electron beams with plasma. Since in this case the radiation frequency is comparable with the plasma frequency, it can be easily adjusted by simply changing the plasma density. The efficient terahertz electromagnetic emission was produced during the injection of relativistic electron beams into plasma in laboratory experiments at the GOL-3 facility INP SB RAS. In this paper the mechanisms of the high efficiency of energy transfer from the relativistic electron beam to the EM radiation in turbulent regime of collisionless plasma are investigated on the base of computer simulation. The kinetic approach for ion and electron plasma components, as well as for electron beam, was used in 2D numerical model with the real mass ratio of charged particles. A parallel electromagnetic particle-in-cell (PIC) code UMKA2D3V was applied to simulate beam-plasma system for parameters close to the parameters of laboratory experiments at GOL-3 facility. Regimes of injection of one electron beam into the plasma and the counter injection of electron beams were considered. Computational experiments were performed using modern computer systems with massively parallel architecture.