Neutral beam injection systems based on RF negative ion sources are the best choice for high power long pulse (steady-state) operation of neutral beam injection systems. The negative ion source is the core component of the neutral beam injection system, which needs to achieve stable negative ion beam extraction and acceleration. During the operation of the negative ion source, the negative ion current will change, especially under long-pulse and high-energy operating conditions, so it cannot meet the requirements of stable operation. To achieve a stable extraction of the extracted beam, the research on beam feedback control was carried out and a beam feedback control system based on RF power adjustment was developed. The beam feedback control system has been applied in the RF negative ion source test platform. The test results show that the beam feedback control system can realize real-time feedback adjustment of the beam to obtain stable extraction of the beam. Beam feedback control based on RF power regulation is feasible, which provides support for the development of high-power RF negative ion sources.