Abstract: This article provides a detailed account of the background, reasons, scope and principles, as well as the design of the new system for the safety-level nuclear island process instrument protection measurement cabinet (KRG-P) renovation of Units 1 and 2 of Qinshan Phase II Nuclear Power Plant. To address the issues of equipment supply disruption and bottlenecks in the old system, and in light of the characteristics of digital transformation of safety-level distributed control system (DCS) of in-service nuclear power plant, the reliability of the equipment and system was comprehensively enhanced through centralized arrangement of purchased components, optimization of quality bits and default values after digitalization, identification of module failure risks, and optimization of the expected transient non-trip cabinet. Through the independent research and development of safety-level hand controllers, it ensures that the safety-level DCS can stabilize the unit status in the event of a severe failure. The above optimization measures can effectively reduce the risk of the implementation of digital transformation of safety-level DCS in nuclear power plants, and also accumulate technical experience for the subsequent digital and domestic transformation of safety-level DCS in nuclear power plants.