Abstract: Synchrotron ring with 24.6 m circumference is main accelerator in Shanghai Proton Therapy Facility. The space for mechanical operation in the ring is very narrow because of many components. The vacuum for synchrotron ring need be better than 1.33×10^-6 Pa. The requirement to vacuum components layout and chamber structure is to contribute to beam uniformity and stability, and to facilitate mechanical assembly. To meet the lattice, vacuum chambers were connected by welding as possible, and the amounts of vacuum components were minimized. The cross section of chamber in BM was rectangular, and in QD and QF was circular. Rectangular chamber and circular chamber were welded by a transitional plate. The chamber in beam splitting region was designed as a fork structure with variable section. The design result shows that the vacuum layout and chamber structure can meet the need of beam running.