Abstract: To reduce impact of equipment rush repair on adjacent region train operation and to ensure personnel safety, it is necessary to reasonably set up SPKS (staff protection key switch) for FAO (fully automatic operation) system in urban rail transit station. Taking a standard station of Nanning Rail Transit Line 5 as an example, by adopting analysis method combining availability and safety, the three setting schemes proposed for SPKS protection area are compared, and scheme 3 with highest overall availability is adopted, which can lower the risk grade to R4.