Thermohydraulic analysis of postulated accidents will identify systems responses to accident scenarios and aid to develop design of safety systems and strategies to prevent and mitigate accident propagation. This paper reports recent progress in analysis of some accident scenarios of a water-cooled fusion DEMO reactor. Four types of accidents are particularly considered: ex-vessel loss-of-coolant of the primary cooling system, in-vessel loss-of-coolant of the first wall cooling pipes, loss-of-coolant in blanket modules and loss-of-vacuum. The analysis has identified responses of the DEMO systems to these accidents, pressure loads to confinement barriers for radioactive materials and radiological consequences. Effectiveness of the safety systems and integrity of the confinement barriers against the accidents are discussed.