A heat dissipation system includes a housing, a circulator and a cooler. The housing has at least one surface made of heat-conductive metal to contact with a heat source. The housing includes a recess with a passage formed on the bottom to contain cooling liquid and an inlet and an outlet connected to the recess. Two pipes are provided to connected between the inlet and the outlet and the cooler, respectively. The circulator is installed in the recess to circulate the flowing of the cooling liquid. As such, heat generated from the heat source is directly conducted to the housing and takes away by the cooling liquid circulated by the circulator to the cooler.