The authors proposed a conception of dynamic operation permission system. The main idea of the dynamic operation permission is to prevent only evident commission errors and to leave operators behave as they like as far as they follow operation manuals and various operation rules. The operation permission is made based on the viewpoints of (1) following the operations specified in operation manuals and (2) suitability of an operation on plant behavior. This study implements the first part of the dynamic operation permission system as an agent composed of an operation database and two software agents on a distributed cooperative environment. The performance of the dynamic operation permission agent is validated by several example scenarios of an abnormal situation of steam generator tube rupture accident of a pressurized water reactor plant.