A fan duct (8) buckled to a fan (7) is mounted in a computer enclosure (4) having an upper panel (44) defining a plurality of apertures (440). The fan duct includes a first open portion (80) having a first opening (804) and a second open portion (82) having a second opening (822). The first open portion comprises two opposite lateral flanges (802). Each flange forms a pair of latches (806, 808) buckled to the fan to prevent removal of the fan duct in the horizontal direction. A pair of resilient tabs (824) is formed at two opposite lateral sides of the second opening. The tabs are pressed by the upper panel of the computer enclosure to confine the fan duct to move upwardly. The second opening communicates with the apertures and the first opening communicates with the fan.