A particle beam guiding system (1a, 1b, 1c) for receiving an incoming particle beam (6a, 6b, 6c) along an incoming trajectory (T1) and controlling an exit energy level and an exit trajectory (T3) of the particle beam, wherein the particle beam guiding system comprises an attenuator (22) for adjusting the energy level of the particle beam； a first beam guide (26) positioned downstream of the attenuator, comprising first and second guiding dipoles, each comprising two magnets for creating magnetic fields for deflecting the particle beam from the incoming trajectory into an intermediate trajectory (T2), wherein the first dipole of the first beam guide is arranged to deflect the particle beam in a first plane, and the second dipole of the first beam guide is arranged to deflect the particle beam in a second plane which is orthogonal to the first plane； and a second beam guide (28) positioned downstream of the first beam guide, comprising first and second guiding dipoles, each comprising two magnets for creating magnetic fields for deflecting the particle beam from the intermediate trajectory into the exit trajectory, wherein the first dipole of the second beam guide is arranged to deflect the particle beam in a first plane and the second dipole of the second beam guide is arranged to deflect the particle beam in a second plane which is orthogonal to the first plane. A radiotherapy system comprising such particle beam guiding systems is also disclosed.
