The invention discloses a synchrocyclotron-based proton heavy ion therapy system. The system is characterized in that the treatment system adopts a synchrocyclotron to accelerate protons or heavy ionsto the highest energy required for treatment; For protons, the maximum energy is 235 MeV. The beam output from the synchrocyclotron enters the high energy transport line for focusing and deflection and is fed to the energy selector. The energy selector makes the beam energy continuously adjustable through the graphite energy reducer. The beam enters a single room and is sent to a rotating gantrysystem, which rotates by +- 185 DEG, allowing the beam to exit in all directions of 360 DEG. Compared with the cyclotron and the synchrotron, the invention can use a magnetic field of up to more than5T to reduce the volume weight of the accelerator, so as to be more compact; And the acceleration voltage requirements are small, reducing the cost of RF system and design difficulties.