A plant alarm system is one of the most important elements of the third layer of independent protection layers (IPLs). Management of the plant alarm system has become identified as one of the key issues because of the disasters caused by alarm floods. The instrumentation, systems, and automation society has proposed an alarm management standard. However, an explicit definition of a business process to properly manage the plant alarm system has not been proposed. A plant alarm system is not always designed using the overall information about the plant, because the concreteness and quantity of the information varies along with the stages of the plant design. The requirements for a safety instrumented system may not be satisfied if the design of the plant alarm system was started after all of the stages of the plant design had been completed. The stages of the plant alarm system design should be carried out concurrently with the stages of the plant design. Therefore, the design process of the plant alarm system should be clarified corresponding to the available information at each stage of the design. To clarify the business process concerned with the plant alarm system, a framework is necessary to express the activities with tools, available information and output. Therefore, a business process model (BPM) as the framework for the plant alarm system will be developed. In this paper, we try to express a BPM concerned with a plant alarm system. Even if the developed BPM is incomplete, the BPM approach will have following merits: design rationale for the plant alarm system can be specified and stored, and the plant alarm system can be designed more logically. The stored design rationale and the logically designed plant alarm system are very useful for management of the change of the plant alarm system and ensuring consistency with other safety instruments.