Abstract: The instrument and control system of Daya Bay Nuclear Power Station is based on analog electronic technology, and it is planned to be digitized during the 30-year overhaul, during which the first-floor analog system will be completely digitized, but the man-machine interface equipment on the second floor will still be controlled by the hard hand operator in the main control room. According to the market research, four transformation schemes of hand operator based on digital system are preliminarily determined. Finally, the overall transformation scheme of developing new hand operator through standard I/O board interface is determined by considering many factors such as functional consistency, product reliability, technical feasibility, development cost, input/output (I/O) signal distribution efficiency and application feedback. This scheme can realize the optimal interface between the hand operator and the transfomed digital system, and effectively improve the utilization efficiency of I/O board channels. At the same time, through the rich software algorithm block function and digital system fault diagnosis function, the improvement measures such as automatic undisturbed switching of actuator and forced manual switching of process signal quality level are added, which effectively improves the reliability and stability of unit equipment control and provides an important reference scheme for similar digital transformation projects.