Maintenance decision making, which is based on a result of imperfect inspection, sometimes causes problems with system operation. In order to reduce opportunities of misjudgment by imperfect inspection, inspection threshold is effective. The impact of component’s failure under the system operation is an important issue on maintenance decision making. It is also important to identify the weaknesses in the system. A minimal path-cut method is a concept that can express the system structure from the functional aspect. In this paper, it derives system importance measures under imperfect inspection using minimal path-cuts, and conduct basic research on the planning of inspection execution plans according to the inspection order.