The study aims to suppress the transient and nonstationary high-SPL (sound pressure level) shock noise. A full-size acrylic model is built up for mimicking the sound field of the control room of a rocket-launching vehicle. For achieving the noise reduction, an adaptive algorithm called the FXLMS is applied to implement the active noise control system. The convergence speed and stability of the FXLMS-type systems depend on the step-size values mainly. They are usually difficult to be decided for fast converging, and keeping the system stable. In the study, the variable step-size algorithms are implemented to automatically select an appropriate step size varying with the system status for desired performance. Experimental results show that the ANC system with the variable step-size algorithm performs well both in complex harmonic and transient high-SPL shock noise environments.