The invention provides a junction box with several switchable function modules. The junction box has a box container providing the input of plurality of external wires. There are several wire connectors positioned inside the box container, wherein each of the wire connector having a first opening and a second opening, each of the second openings is provided for accommodating one of the external wires. In addition, a box cover having a function module is provided for being mounted on the box container. Once the box cover being mounted on the box container, plurality of contact pins set on the box cover would be inserted into the first openings of the wire connectors then the contact pins would be in electrical communication with the external wires. Therefore, the function module, which is in connection with the contact pins, would be activated.