A cover assembly comprising a heat dissipation cover and an exhaust manifold heat dissipation cover coupling device for thermal stress and vibration deflection, the device comprising: an inner bush having a through-center portion and being coupled to a lower portion of a coupling hole formed at the heat dissipation cover; an outer bush having a through-center portion and being coupled to an upper portion of the coupling hole formed at the heat dissipation cover; an inner mesh elastic body having a through-center portion and disposed under the inner bush; an outer mesh elastic body having a through-center portion and disposed over the outer bush; an inner collar having a through-center portion and disposed under the inner mesh elastic body; and an outer collar having a through-center portion and disposed over the outer mesh elastic body, wherein the inner bush has a bush protrusion and the outer bush is formed in a hollow disc shape; wherein the inner mesh elastic body and the outer mesh elastic body are made of the same material as the inner bush and the outer bush, the inner mesh elastic body and the outer mesh elastic body attenuate vibration and prevent wear of the heat dissipation cover by independently sliding only on contact surfaces of the inner bush and the outer bush, respectively, and wherein the inner collar and the outer collar are coupled to each other, characterized in that the bush protrusion of the inner bush is formed by the through-center portion; and the bush protrusion of the inner bush is bent so that it is coupled to the heat dissipation cover while pressing an edge of a center portion of the outer bush, so that an interface between the end of the bent bush protrusion of the inner bush and the outer bush is formed on an inner surface of the through-center portion of the outer bush not to protrude from a top of the outer bush. an inner bush having a through-center portion and being coupled to a lower portion of a coupling hole formed at the heat dissipation cover; an outer bush having a through-center portion and being coupled to an upper portion of the coupling hole formed at the heat dissipation cover; an inner mesh elastic body having a through-center portion and disposed under the inner bush; an outer mesh elastic body having a through-center portion and disposed over the outer bush; an inner collar having a through-center portion and disposed under the inner mesh elastic body; and an outer collar having a through-center portion and disposed over the outer mesh elastic body, wherein the inner bush has a bush protrusion and the outer bush is formed in a hollow disc shape; wherein the inner mesh elastic body and the outer mesh elastic body are made of the same material as the inner bush and the outer bush, the inner mesh elastic body and the outer mesh elastic body attenuate vibration and prevent wear of the heat dissipation cover by independently sliding only on contact surfaces of the inner bush and the outer bush, respectively, and wherein the inner collar and the outer collar are coupled to each other, characterized in that the bush protrusion of the inner bush is formed by the through-center portion; and the bush protrusion of the inner bush is bent so that it is coupled to the heat dissipation cover while pressing an edge of a center portion of the outer bush, so that an interface between the end of the bent bush protrusion of the inner bush and the outer bush is formed on an inner surface of the through-center portion of the outer bush not to protrude from a top of the outer bush.