A flight control system of an aircraft and a flight control method of the aircraft are provided in which the overrunning an operation limitation on a flight condition can be prevented even when a pilot operates a flight control device fast. The flight control system of the aircraft includes a flight control device; a sensor configured to detect a first parameter changed based on a flight condition of the aircraft; a limitation flight control position calculating section configured to calculate a limitation flight control position of the flight control device when the first parameter reaches a limitation value, based on the first parameter; a reaction force generating actuator configured to change a reaction force which the pilot receives when carrying out a flight control input to the flight control device, in response to a reaction force generating command generated based on the flight control position of the flight control device and the limitation flight control position; an inner loop command calculating section configured to generate an inner loop command based on the flight control position; and a control surface actuator configured to drive a control surface of the aircraft based on the flight control position and the inner loop command.