Abstract: Support system initiating event (SSIE) is a special type of initiating event and should be treated appropriately in the probability safety assessment (PSA). The important technique issues to be addressed in modeling include: PSA modeling linking and quantification methodology, mission time for the standby trains or components, common cause failure (CCF), importance and uncertainty analysis results. The treatments method of these issues was revealed inconsistent for different analyzers and influenced the risk insights of PSA significantly at the present time. Based on the requirements of technical standards, this paper put forward the following suggestions through case analysis and comparison: a. SSIE fault trees should be linked with PSA overall model and quantified; b. Currently two common methods-Multiplier and Explicit are both available. However, the limitations of the two methods in the analysis of importance and uncertainty should be understood, and obvious deviations should be avoided.