The design process of High Impedance Surface (HIS) is a challenge in realizing low-profile antenna. To carry out properly this process, a 3D-electromagnetic simulator is required. This paper shows an overview of the different numerical techniques which can be applied to simulate the behaviour of an HIS using CST Microwave Studio ® (CST MWS). The considered HIS is composed of a metallic square patches array printed on the top of a metal backed substrate. To demonstrate the validity of the different solvers used, some measurements of the dedicated structure have been performed in a waveguide simulator.