Abstract: The High Pressure Injection System (HPIS) of Qinshan Nuclear Power Plant isone of the most important enginering safety features. It can be used to mitigate theconsequence of loss-of-coolant accidents. The reliability analysis for this system isperformed with the fault-tree analysis method. The component failure modes andthe failure data is taken from "Generic Data Base for PSA of Qinshan NuclearPower Plant", which is compiled on the basis of the generic data base publishedin American Literature IREP. In this analysis, the computer code package RALLYdeveloped by GRS (F.R.G) is used. This analysis consists of the calculation of thesystem unavailability, uncertainty analysis (interval estimation), statistics estimation,and importance analysis. The result shows that this system has high reliability.According to the analysis results, the relative weak points of the system are foundand the system design will be further improved.