Traditionally, the introduction of automation into the process systems of nuclear power plants has been made by conservative way in order to maintain plant safety during accident situation. However, recent development of the advanced information technology allows us to reconsider what the automation during the accidents should be and how automation system should work together with the interaction with human. This paper concerns the way of automation during the accidents with some specific examples of several automation levels defined in this paper. The acceptable human-machine interaction is also suggested when the automation is advanced to the extent that human does not necessarily take recovery actions.