A mounting apparatus includes a bracket and two shafts. The bracket includes a fixing plate defining a number of horizontally arranged vents, for mounting a number of fans to the rear side of the fixing plate, with each vent aligning with one of the fans. The shafts are respectively and horizontally mounted to a top and a middle of a front side of the bracket. A number of shield plates are rotatably connected to the shafts. The shield plates hang vertically under the corresponding shafts by gravity. Each of the vents is covered by two vertically aligned shield plates upon a condition that the gravity of the two shield plates are not overcome by airflows passing through the vents.