A heat dissipation assembly includes a bottom plate, an outer cover, a heat guiding base, a flow-acceleration unit and two side cover sets. The bottom loads a heat-generating source. The outer cover includes a cover body and two slots. The cover body covers the bottom plate to define an accommodation space therebetween, and the slots are oppositely formed on the cover body and connected to the accommodation space. The heat guiding base thermally contacts the heat-generating source and the cover body, and is formed with voids arranged alongside, each of the voids is communication with the slots respectively. The side cover sets are disposed within the slots, respectively, and detachably connected to the cover body and the heat guiding base. The flow-acceleration unit is disposed in one of the side cover sets to lead a fluid to the other through the voids.