A heat dissipation system includes an enclosure, and a mainframe module enclosed in the enclosure. The mainframe module includes a baseboard with a motherboard and a mass storage device attached to the baseboard, a first cooling fan mounted on a top surface of the motherboard, and an air guiding panel attached on the baseboard surrounding the mass storage device. The air guiding panel guides cool air to the mass storage device along a first direction and out of the mainframe module by the first cooling fan in a second direction perpendicular to the first direction.