Abstract: After long-term operation, the 10 MW High Temperature Gas-Cooled Reactor (HTR-10) full digital operation instrumentation and control (I&C) system faced a series of problems, such as components ageing, performance degradation, shortage of spare parts and poor extensibility. By analyzing the system’s technical characteristics and existing problems, the system updating principles, goals and detailed scheme in the network architecture, hardware configuration and function optimization were presented. The updated system will effectively improve the system security and stability.