Recently in U.S. and Europe, the approach for the safety of plant intensifies because of many accidents in plant. In the approaches, alarm system is especially important. Alarms should be used to enable operators to diagnose faults of plant and plan countermeasures. To accomplish these functions, nuisance alarms should be eliminated. In this study, we suggest a systematic method of alarm system design for unsteady state process by using Cause-Effect model. The presumed indicators were chosen from intended indicators are theoretically guaranteed to be able to qualitatively distinguish all assumed faults. And by use of the different model for each process in unsteady state operation, it is considered that fault candidates and indicators are restricted. The method is applied to a simple process for the case study.