RCS is very significant to confirm data for target designation. The targets signature is different, because every target has own signature, and this specific signature is utilized to recognize the type of structure which will be tested. The monostatic radar utilizes one antenna on the body for reducing the scattering of signals for given polarization and receive and transmit in this type in the same location. Microstrip patch antenna is widely used in microwave systems, especially for space applications. In this paper, rectangular microstrip antenna in c-band frequency is designed and simulated as a target to calculate monostatic RCS area using CST software 2019. The strip antenna is simulated and modeled for different target angles (0, 45, 60and 90) degree. The monostatic radar cross section is simulated at 8GHz with incident angles from 0-180 degree. The best RCS of rectangular patch antenna is about -31m2 at the incident angle θ=60o.