[en] To increase charged particle beam energy the method of ring beam accumulation in varying guiding magnetic field is suggested. According to the above method a charged particle beam is transported into the region of guiding magnetic field onto the relativistic orbit with the limit radius by decreasing the guiding magnetic field. Then microwave field with azimuthal component is generated on this orbit. Then the guiding magnetic field value is restored to its initial value, microwave field being present. After this the operation sequence is repeated till obtaning the accumulated beam current specified value. Therewith the microwave field is conserved during the whole accumulation period. The accumulated beam energy increase is due to increase of the beam radius. Estimations of the beam parameters when using the suggested method for the ''Troll'' synchrotron are presented