In this paper, a gain-scheduled equivalent-cascade internal-model-control (IMC) tuning method for water level control system of nuclear steam generator is presented. First, a water level control system for a steam generator is transferred into an equivalent cascade-feedforward control system. Second, analytical tuning rules for the equivalent cascade control system are derived based on the IMC-(proportional-integral-derivative) PID method, which can simultaneously tune the primary/secondary loops and avoid the re-identification step. Finally, gain scheduling is performed to eliminate the influence of process nonlinearity. The experimental results of nuclear simulation platform have demonstrated the superiority of the proposed tuning method.