Abstract: The aim of this paper was to analyze the impact of rectangular plane ground on the radiations pattern of the monopole antenna. Several simulations have been performed where the monopole antenna with wavelength 4m was placed on top of the rectangular plane ground and then radiations pattern was obtained in terms of directivity, electric field and gain, and finally the results were analyzed and concluded that large the ground plane is, the lower the direction of maximum radiation and as the ground plane approaches infinite size, the radiation pattern approaches a maximum in the x-y plane.