A portable electronic device and a one-hand touch operation method thereof are provided. A touch operation performed on a touch screen is detected. When a shift amount of the touch operation in a first direction is greater than a first threshold, whether to activate a one-hand mode is determined according to a shift amount of the touch operation in a second direction. When the one-hand mode is activated, the operation interface image is zoomed out or shifted, and displayed in a one-hand mode interface display region.