Upper mounting structure of rear strut assembly

An upper mounting structure of a rear strut assembly to which the load of the rear strut assembly is transmitted forms a polygonal section (c) for increasing the rigidity, thereby effectively reducing the load-concentration transmitted to a wheel housing cover (52) via the rear strut assembly, decreasing running noise and idle noise, improving the NVH function, and shortening the workload by reducing the number of components, and increasing the rate of the fuel consumption.