A backlight source includes light bars, adapter plate(s) and connection structures. Each light bar includes light-emitting group(s) and external connection unit(s). Each external connection unit is electrically connected to at least one light-emitting group and included at least one first electrode pair. Each adapter plate includes adapter circuits, each adapter circuit includes adapter units, each adapter unit includes at least one second electrode pair. Ends of each connection structure are electrically connected to one external connection unit and one adapter unit. All second electrode pairs of adapter units of a same adapter circuit are classified into at least one group, each group includes second electrode pairs electrically connected in series. In light-emitting groups electrically connected to adapter units of the same adapter circuit, light-emitting groups electrically connected second electrode pairs in a same group are connected in series to form a dimming region.