At present, probabilistic safety analysis (PSA) has been widely used in many fields such as the design and manufacture of nuclear power plants, and PSA has gradually developed into an important tool for safety evaluation and decision-making. With the increasing peak-to-valley difference between power grid loads, the peak-shaving situation of the power system is becoming more and more severe. Due to the increase in the proportion of nuclear power in the power grid, the power system has an increasing demand for nuclear power units to participate in power grid peak-shaving. The nuclear power plant technical specifications and the nuclear power plant final safety analysis report in the nuclear safety regulations have clear requirements for the operating conditions of the nuclear power plant. As a power generation device with special safety requirements, the safest and most economical operation mode of nuclear power plants is to operate at rated load. The Chinese government and nuclear safety regulatory authorities attach great importance to nuclear power safety, and nuclear safety must be foolproof. From the perspective of probabilistic safety analysis, this paper analyzes the impact of Fangjiashan Nuclear Power Plant’s (FSJ NPP) participation in peak-shaving by using the load-following operation mode, and gives reasonable suggestions.