Due to the existing serious climate and environment problems caused by burning fossil fuels, nuclear energy is now under rapid development. As a crucial technology in the field of nuclear energy, power-level control for nuclear power plants is significant for not only regular operating but also safety issues. A nonlinear controller based on feedback dissipation and backstepping (FDBC) is presented in this paper. This new controller can guarantee not only globally closed-loop asymptotic stability but also robustness to the uncertainties of the control rod dynamics. Numerical simulation results show the high performance of this controller. Moreover, this newly built controller is simplified to a proportional power-level controller under the assumption of no modeling error in control rod dynamics. The characteristics of these two power-level controllers are given by theoretic analysis and numerical simulation.