A heat dissipation air duct is provided. The air duct is fixed inside a
computer case, and covers a plurality of high heat-generating elements on
a mainboard. The air duct includes a main air duct and an auxiliary air
duct. The main air duct isolates a first air duct area inside the
computer case, and an air inlet is formed in a side of the air duct area.
The auxiliary air duct is fixed on the bottom of the main air duct, and
is accommodated in the first air duct area, so as to further isolate a
second air duct area in communication with the air inlet it the first air
duct area. One of the pluralities of high-generating elements is covered
by the auxiliary air duct, and is accommodated in the second air duct
area.