A synchrotron-based proton therapy (PT) facility that conforms with the requirement of future development trend in compact PT can be operated without an energy selection system. This article demonstrates a novel radia-tion shielding design for this purpose. Various FLUKA-based Monte Carlo simulations have been performed to validate its feasibility. In this design, two different shielding scenarios (3-m-thick concrete and 2-m-thick iron–concrete) are proved able to reduce the public annual dose to the limit of 0.1 mSv/year. The calculation result shows that the non-primary radiation from a PT system without an inner shielding wall complies with the IEC 60601-2-64 inteational standard, making a single room a reality. Moreover, the H/D value of this design decreases from 2.14 to 0.32 mSv/Gy when the distance ranges from50 to 150 cm from the isocenter, which is consistent with the previous result from another study. By establishing a typical time schedule and procedures in a treatment day for a single room in the simulation, a non-urgent machine maintenance time of 10 min after treatment is recom-mended, and the residual radiation level in most areas can be reduced to 2.5μSv/h. The annual dose for radiation therapists coming from the residual radiation is 1 mSv, which is 20％of the target design. In general, this shielding design ensures a low cost and compact facility compared with the cyclotron-based PT system.