Abstract: A novel reactor vessel internals (RVI), which a barrel assembly is fixed by the compression barrel assembly, and hang in the middle of reactor pressure vessel (RPV), was proposed by analyzing the structure characteristics of China small modular reactor (ACP100). This structure has many advantages, such as easy for manufacture and installation, good sealing performance, and well flow distribution capability. The results of mechanical analysis and control rods drive line comprehensive experiment and flow-induced vibration test show that it is with high security and reliability, and fully meets the functional requirements of ACP100.