A circuit structure for a lamp set which includes a socket, a lamp assembly mounted onto the socket and an electrode portion. The lamp assembly surrounds a housing space inside to hold a power distribution dock connecting to the socket. The power distribution dock has a holding space to hold a power conversion element which is electrically connected to the electrode portion to receive external electric power and transform to starting power to drive the lamp assembly to generate light. The power distribution dock and the power conversion element are located in the housing space. Thus the total height of the socket is reduced and the lamp set can be shrunk to a smaller size.