[en] Electrostatic beam focusing system for the JINR phasotron is described. The system is mounted into the centre of accelerator for reducing particle losses in axial motion. The peculiarity of the system is an alternating focusing. It is realized due to dummy dee modification by introducing the radial focusing gaps. The focusing electrode is at a constant negative voltage. Using the electrostatic focusing system allowed one to decrease twice effective dimension of beam and to reduce Z-losses of particles. As a result, the beam intensity increased by 1.5 times for amplitude of accelerating voltage of 40 kV. Maximum internal beam intensity achieved was 9.2 mkA with rotation velocity of frequency variation of 2400 turns/min