The invention belongs to the technical field of accelerators, and discloses a multi-mode tuning method for medical cyclotrons. The method comprises that after a
radio frequency system is started and turned into a continuous running state, a
phase locking loop (PLL) tracking cavity resonant frequency mode is used for tuning, and a
fine tuning capacitance plate is placed in the middle of an adjustment
stroke; when PLL frequency update tuning operates for 5 minutes to 10 minutes, a
digital signal processor controls to switch an
analogue switch, the
fine tuning capacitance plate is converted from position feedback to
capacitance plate tuning, and simultaneously, the PLL uses a current frequency value as a starting point and a final working frequency value as an ending point, and the frequency is reduced to working frequency and fixed in a mode with 0.002 MHz of stepping and an interval of 1s; and capacitance plate position signals are monitored continuously, a
stroke intermediate point serves as a reference, protection points are arranged at 4 / 5 positions on the left and right, and the capacitance plate is fixed after being adjusted by the PLL when surpassing the positions. According to the multi-mode tuning method for medical cyclotrons, a whole process of
radio frequency starting and running can be covered completely and conveniently, and the whole
machine time utilization efficiency is improved.