Limited human attention resources produce cognitive load and so critical human error. In particular, the case of large-scale systems due to human error from the limited attention resources had often very large accidental damage. Recent disaster of Fukushima Daiichi nuclear power plant is a typical example. Display design method to reduce the cognitive load has been studied in the area of Ecological Interface Design (EID). EID method proposed Work Domain Analysis (WDA) for understanding work domain constraints. Using WDA method, it analyzed Steam Generator and Pressurizer Water Level control process design of digitalized Main Control Room.