A heat sink includes a heat dissipation fins assembly, a heat spreader, and a heat pipe. The heat dissipation fins assembly includes a plurality of heat dissipation fins. A guide plate extruding from a bottom of each of the heat dissipation fins. The guide plate being connected to an adjacent heat dissipation fins. The heat dissipation fins are connected in series by the guide plate thereby defining a number of air channels. Each heat dissipation fin includes a through hole defined therein and aligned with each other. The heat spreader is disposed under the heat dissipation fins assembly and a through groove is formed in the heat spreader. A heat pipe passes through the through hole and the through groove. The heat sink has improved heat dissipation efficiency.