Abstract: Proton beam window (PBW) is a critical component of the China accelerator-driven system (C-ADS), which will isolate the accelerator vacuum from the target. Scattering effect induced by material of the PBW and the cooling medium is the most important factor causing the beam loss out of the target. Very high energy deposition and irradiation load of the PBW make the thermal hydraulic research especially indispensable. For beam window with multiple pipe structure, calculation results show that lost particles can be controlled within 1% when the beam window is located at 1.5 m from the target. The stress induced by heat load and cooling medium as well as pressure difference over the PBW can be controlled within permissible stress of present selected material. Primary parameters of the PBW of C-ADS are also given through analysis and discussion.