Abstract-The growing requirements of steel products qualities bring even tricky restrictions to the rolling process. With the fast response, reliable control and low maintenance requirements, the hydraulic automatic gauge control system has been widely applied to screw down the roller to maintain the precise rolling spaces for product quality control. Regarding to non-stopped heavy duties charged to the system, unavoidable faults and disfunctions not only influence the product quality, but also bring underlying safety issues. The hydraulic cylinder is the executing component of the roller screw down and it has the dominant percentage of hydraulic components' faults. Working with unexpect loading is one of major impact factor that causes several chain-effects happened to the cylinder, as the classical diagnostic process is lack of cross-validating and time-consuming, the paper proposes the potentials of using acoustic emission to fill the dilemmas. The works include the data acquisition process to record the ultrasound acoustic signals from the hydraulic cylinder during it was loaded with 6 types of conditions, a modified image based acoustic emission approach constructed by using 8 significant waveform features was applied to generate visual effects and transform the cylinder acoustic emission signals under various loadings to a uniform format, the subtle differences among various loadings can be observed based on the pixel and intensity changes of the images. By applying the principal component analysis to project the acoustic emission image profiles onto the 3D plane, a clear trajectory can be observed with normal and overload conditions allocated upon the positive and negative sides of the axis. The result provided not only the potential of using acoustic emission for dynamic state identification of the subtle changes, but also opens up the possibility of preventive measures to the cylinder at risks in the future.