A portable electronic device includes a main body, a flip cover, and a hinge assembly. The flip cover is rotatably fixed on the main body via the hinge assembly. The hinge assembly includes a sensing module, a hinge mechanism, and a microcontroller. The sensing module is configured to detect control signals. The hinge mechanism is configured to control an angle between the flip cover and the main body. The microcontroller is electrically connected to the sensing module. The microcontroller receives the control signals from the sensing module, and controls the hinge mechanism to rotate to a specified angle according to the control signals. The angle between the flip cover and the main body is automatically adjusted correspondingly.