The disclosure provides a liquid-cooling heat dissipation device. The liquid-cooling heat dissipation device is configured to be in thermal contact with an expansion card. The liquid-cooling heat dissipation device includes a base plate, a thermally-conductive component and a heat exchanger. The base plate is configured to be mounted on the expansion card. The thermally-conductive component is mounted on the base plate. The thermally-conductive component and the base plate together form a liquid chamber therebetween. The heat exchanger is mounted on the base plate and connected to the liquid chamber.