A power supply mechanism for a long-stroke seat, comprising: a wire harness accommodation box having at least one accommodation space and at least one opening in communication with the accommodation space; a drag chain having a wire harness channel, wherein the drag chain is bent and accommodated in the accommodation space, a first end of the drag chain is relatively fixed to the wire harness accommodation box, a second end of the drag chain passes through the opening and is slidably disposed in a slideway of a lower slide rail of the seat, and two ends of the wire harness channel pass through two ends of the drag chain; and a wire harness threaded in the wire harness channel, wherein a first end of the wire harness passes through a first end of the wire harness channel and the opening to be connected to a power supply, and a second end of the wire harness passes through a second end of the wire harness channel to be connected to an upper slide rail of the seat which is slidably mounted on top of the lower slide rail, wherein a drag chain adapter is connected to the opening of the wire harness accommodation box, wherein the drag chain adapter has an inner turning channel for the drag chain to pass through, the inner turning channel extends through a first side portion and a second side portion of the drag chain adapter, the first side portion is connected to the opening, the second side portion is connected to the lower slide rail of the seat, and the inner turning channel is in communication with the slideway of the lower slide rail of the seat, wherein a rail slot having an upper opening is provided on the second side portion of the drag chain adapter, an end of the lower slide rail is vertically snap-fitted into the rail slot, and the upper opening of the rail slot is covered by a slide rail end cover. a wire harness accommodation box having at least one accommodation space and at least one opening in communication with the accommodation space; a drag chain having a wire harness channel, wherein the drag chain is bent and accommodated in the accommodation space, a first end of the drag chain is relatively fixed to the wire harness accommodation box, a second end of the drag chain passes through the opening and is slidably disposed in a slideway of a lower slide rail of the seat, and two ends of the wire harness channel pass through two ends of the drag chain; and a wire harness threaded in the wire harness channel, wherein a first end of the wire harness passes through a first end of the wire harness channel and the opening to be connected to a power supply, and a second end of the wire harness passes through a second end of the wire harness channel to be connected to an upper slide rail of the seat which is slidably mounted on top of the lower slide rail, wherein a drag chain adapter is connected to the opening of the wire harness accommodation box, wherein the drag chain adapter has an inner turning channel for the drag chain to pass through, the inner turning channel extends through a first side portion and a second side portion of the drag chain adapter, the first side portion is connected to the opening, the second side portion is connected to the lower slide rail of the seat, and the inner turning channel is in communication with the slideway of the lower slide rail of the seat, wherein a rail slot having an upper opening is provided on the second side portion of the drag chain adapter, an end of the lower slide rail is vertically snap-fitted into the rail slot, and the upper opening of the rail slot is covered by a slide rail end cover.