A smart ultra box adapting to a protective case is disclosed. The protective case protects a mobile communication device. The ultra box comprises a main body, a conversion unit and a flexible printed circuit board. The main body has a power output interface and an external power interface. The conversion unit disposes at the main body, to electrically connect the power output interface and the external power interface. The flexible printed circuit board electrically connects to the conversion unit, the flexible printed circuit board extending outwardly from the main body. The external power interface receives a commercial power source. The conversion unit converts the commercial power source into a first electric power and a second electric power. The power output interface output the first electric power, and the flexible printed circuit board transmits the second electric power.