The central (gas/chemical) supply systems of wafer factory were studied by analysis abnormal events. This paper refers to this wafer factory characteristic using the FMEA method to set up the boundary condition of risk assessment. This research emphasizes on exploring and analyzing the frequency and causes by used FMEA risk assessment of the abnormal events. Follow the final conclusion of the study will can to prevent and improve for reduction of abnormal rate and reference of troubleshooting.