Abstract: To ensure the independence and reliability of the safety-class Distributed Control System (DCS) following the digital transformation of the protection and measurement cabinets (KRG-P) in Units 1 and 2 of Qinshan Phase II Nuclear Power Plant, a three-dimensional coordinated isolation scheme featuring Physical Separation-Electrical Isolation-Communication Isolation and a matching decoupling design are proposed in response to the mutual interference issues between systems of different safety classes and redundant groups. The isolation design encompasses three key aspects: physical separation between redundant protection groups and devices of varying safety classes; electrical isolation based on optical fiber transmission, circuit breakers, filters, and PIPS modules (optical/amplifier/converter); and communication isolation via independent links among redundant groups. Customized isolation interfaces are designed for Level 0–2 systems and third-party systems, with decoupling realized through optical fiber transmission or relay hardwiring. The scheme can ensure the stable execution of safety functions by safety-class systems under design basis events, thereby providing a key technical reference for the digital transformation of safety-class DCS in nuclear power plants.