A lamp assembly includes a lamp and a junction box. The lamp defines a front chamber and a rear chamber. A plurality of LED modules is received in the rear chamber. A receiving member is located at a top of the front chamber. The junction box is mounted on an outside of the receiving member. A junction base is received in the junction box. A mounting tube extends through the junction box and the receiving member of the lamp to mount the junction box on the lamp. A connecting tube is mounted on the junction box. Wires of the LED modules extend through the mounting tube and connecting with the junction base. The connecting tube is adapted to receive wires extending from an outside power sources to the junction base.