The analysis of particle motion from the injection region up to the final radius of the JINR high current phasotron is given. The purpose of the investigation was the appreciation of the beam quality and intensity. Synchrotron and betatron radial and vertical particle motion as well as space charge repulsion were included into the computer code for beam investigation. As a result, the beam intensity earlier appreciation of 40-45 ¿ A was confirmed, magnetic field tolerances in the first phase oscillation region were obtained and the required time dependences of acceleration voltage amplitude were refined.