A system operation support device in a power system stabilizes the power system and has a predicted accident time system state calculation unit that receives measured data, a system topology, and a target accident type as inputs, and calculates a system state and a predicted accident time system state. A control menu calculation unit receives the results of the predicted accident time system state as inputs and calculates a control menu. A restoration control means calculation unit receives the result of the control menu calculation as an input and calculates a restoration control procedure. A restoration prevention control procedure calculation unit receives the result of the restoration control and a target restoration time parameter as inputs and performs a power generator output adjustment time simulation, a necessary prevention control amount calculation, and a prevention control procedure calculation. A display unit displays the restoration control procedure and the prevention control procedure.