Abstract: In response to the issues of positioning and threshold setting for the KRT system alarm function, a series of analysis and research were carried out in the design of the Fangchenggang Phase Ⅱ project. The KRT alarm threshold design and demonstration process of “operating condition analysis-function and strategy determination-consequence assessment-alarm threshold setting” was established, and based on the design logic, multiple comprehensive KRT alarm thresholds were reasonably and conservatively determined. This solved the engineering concerns and improved the safety of radiation monitoring in the nuclear power plant.