Yin, M. An, S. Guan, F.P. Lv, Y.L. Pan, G.F. Wang, F. Wei, S.M. Wen, L.P. Zhang, T.J. Zhu, F.Zhu. JACoW Publishing Geneva, Switzerland 978-3-95450-205-9 10.18429/JACoW-Cyclotrons2019-MOP008 English 42-44 MOP008 dipole proton quadrupole vacuum cyclotron Contribution to a conference proceedings 2020 2020-06 https://doi.org/10.18429/JACoW-Cyclotrons2019-MOP008 http://jacow.org/cyclotrons2019/papers/mop008.pdf To develop the proton beam transfer system which used in the field of proton therapy, the mechanical design of proton beam lines based on the CYCIAE-230 has been finished at the China Institute of Atomic Energy (CIAE). The proton beam transfer system includes the beam lines, beam dump, gantry, nozzle, couch, image guidance system, etc. Two beam lines are designed at CIAE this moment. One is for the nozzle system, the other is for the beam dump. The beam lines include four systems: the energy selection system, the beam transportation systems, gantry system, beam dump. The beam lines are very compact in order to match the beam optics and the space limitation. The gantry can be rotated ±180°. There are several key components in beam lines, such as magnets, degrader, beam diagnostics component, vacuum component, etc. The designed mechanical tolerance of the magnets is limited less than 0.1 mm. There are at least four targets on each magnets for collimation and all the components can be adjusted in three dimensions. The magnets are being manufactured now. The mechanical design of proton beam lines based on the CYCIAE-230 will be presented in this paper.