A negative ion source acts as a critical part in a neutral beam injector (NBI). A high current ion source is required for the high-power NBI. In this paper, a prototype radio frequency (RF) ion source and its test facility are developed in the Institute of Plasma Physics, Chinese Academy of Sciences, to demonstrate the key technology of the high power negative ion source. The structure design of the RF negative ion source is presented, involving the designs of the ion source plasma generator and accelerator. The detailed structure design and analysis of the key parts of the ion source are also presented, such as the Faraday shield (FS) and accelerator grids. The fluid-thermal-structural coupling characteristics of the FS and grid are explored with different mechanisms of fluid pressure, RF power, and the structure type on the thermal stress. Then, the processing and manufacturing scheme of the FS and grids are also given. Finally, the results were presented with a manufactured three cooling channel FS. The experimental results prove that the developed structure design of the RF ion source is effective and reliable, and the correctness of finite element analysis is also verified by experimental data comparison.