Abstract: Load-following model of PWR nuclear power plant （NPP） can correspond with unit product and electric network demand, prolong circle life of fuel and enhance economical performance of unit operation. The characteristic of nuclear reactor is high complex, nonlinearity and time-vary. The nuclear reactor system model of lumped parameter was built based on reasonable reduction, and control strategy of load-following was designed. Under phase step and linearly varying load disturbance, the characteristic of nuclear reactor load-following control system was analyzed. The results show that characteristic of control is consistent with practice, and control system is satisfied with the performance demand of load-following.