In this paper, active disturbance rejection control (ADRC) is applied to the vibration control of the all-clamped plate structure with an inertial actuator. Knowing that modeling uncertainties, dynamic nonlinearities and multivariable couplings are often the major causes of a downgrading performance and instability, a cascade ADRC controller is, hence, utilized to mitigate the effects of these issues. The dynamics regarding the all-clamped plate structure and inertial actuator are obtained through theoretical analysis and experimental testing. Furthermore, the real-time control experimental verification is carried out on the hardware-in-the-loop platform based on the NI PCIe-6343 data acquisition card. The comparative experimental results show that the proposed cascade ADRC controller has a better vibration suppression performance, disturbance rejection performance and decoupling ability.