A heat dissipation assembly mounted to a main board in a blade server includes a graphics card, a heat sink, and a thermal board. The graphics card includes a GPU and a plurality of first graphics memory chips mounted on a top thereof, and a plurality of second graphics memory chips mounted on a bottom thereof. The heat sink for cooling the GPU and the first graphics memory chips, includes a base attached to the top of the graphics card, a finned part fixed to a top of the base, and a heat pipe sandwiched between the base and the finned part. A pathway of the heat pipe passes over the GPU and at least part of the first graphics memory chips of the graphics card. The thermal board is mounted to the bottom of the graphics card for cooling the second graphics memory chips.