A load-following operation system for a nuclear reactor load-following operation including boron concentration adjustment, the load-following operation system comprising: a boron concentration control unit for adjusting a boron concentration, the boron concentration control unit comprising a boron concentration determination unit for determining a boron concentration on the basis of input first operation information comprising the current boron concentration, the target power, and the target power distribution and a boron concentration adjustment unit for adjusting a boron concentration according to the determination of the boron concentration determination unit; and a control rod control unit for controlling a control rod, the control rod control unit comprising a control rod determination unit for determining a control of the control rod on the basis of input second operation information comprising target power, target power distribution, and current control rod position and a control rod driving unit for controlling the control rod according to the determination of the control rod determination unit, characterized in that the first operation information includes a set core temperature and an operating core temperature, and further an axial power distribution setting value of a core and an axial power distribution operation value of the core, and the boron concentration control unit is adapted to adjust the boron concentration when a difference between the set core temperature and the operating core temperature is a certain level or lower and a difference between the axial power distribution setting value and the axial power distribution operation value is a certain level or higher. a boron concentration control unit for adjusting a boron concentration, the boron concentration control unit comprising a boron concentration determination unit for determining a boron concentration on the basis of input first operation information comprising the current boron concentration, the target power, and the target power distribution and a boron concentration adjustment unit for adjusting a boron concentration according to the determination of the boron concentration determination unit; and a control rod control unit for controlling a control rod, the control rod control unit comprising a control rod determination unit for determining a control of the control rod on the basis of input second operation information comprising target power, target power distribution, and current control rod position and a control rod driving unit for controlling the control rod according to the determination of the control rod determination unit, characterized in that the first operation information includes a set core temperature and an operating core temperature, and further an axial power distribution setting value of a core and an axial power distribution operation value of the core, and the boron concentration control unit is adapted to adjust the boron concentration when a difference between the set core temperature and the operating core temperature is a certain level or lower and a difference between the axial power distribution setting value and the axial power distribution operation value is a certain level or higher.