Against the backdrop of the “dual-carbon” strategy, nuclear power capacity has expanded significantly. From the perspective of national security, nuclear safety must always be prioritized. However, with the continuous decline in the cost of other clean energy sources, the economic efficiency of pressurized water reactor (PWR) technology urgently needs to be improved. It is of great significance to absorb, master, integrate, and transform international large-scale advanced PWR technology. The VVER reactor, one of the three main PWR types introduced in China, combines safety and economy, enhancing the overall advanced level of nuclear power plants. As a supplement to the shutdown protection system, the integrated pre-protection system (PPS) of the VVER reactor design stabilizes unit parameters by limiting reactor power when process parameters deviate or major equipment fails, thereby reducing unplanned shutdowns and significantly improving the economic efficiency of nuclear power plant operations. This paper introduces the design and implementation of the PPS from the perspectives of system function, system architecture, interface design, typical logic processing, and fault safety, based on the functional attributes of the domestically developed FirmSys safety-level DCS platform. Adhering to the relevant requirements of defense-in-depth and safety-level DCS design principles in regulations, the system has been verified through reliability analysis. The design and implementation of the pre-protection system have been successfully applied to Tianwan Units 7&8 and Xudapu Units 3&4, providing a reference for the design and implementation of the second-level defense-in-depth protection system of nuclear power plants.