The disclosure provides a storage medium, an expansion base and an operation method thereof combined with a portable electronic device. The portable electronic device is pre-installed with an application program and includes a touch screen. The expansion base is paired with the portable electronic device and accommodates the portable electronic device. When the portable electronic device is accommodated inside the expansion base, a touch window on the surface of the expansion base exposes at least a portion of the touch screen, and the portable electronic device executes the application program to automatically adjust a size or a display position of a display image of the touch screen to correspond to the touch window.