In order to meet the demand for miniaturization and excellent performances of antennas to send and receive the wireless signals, in this paper a novel Photonic Band Gap (PBG) structure of a two-dimensional square lattice array etched on one side of silicon wafer is proposed as the grounds of a microstrip patch antenna. An analysis of the performance of a patch antenna with a PBG ground has been carried out, then two rectangle MEMS microstrip antennas with a conventional and a PBG ground respectively, are designed, while the alternating direction implicit finite-difference time-domain (ADI-FDTD) is adopted to perform time simulations of Gaussian pulse propagation in the microstrip antennas, as a result of the versatile method, the frequency-dependent scattering parameters and input impedance could be derived. An important reduction of the surface waves in the PBG antenna has been observed in the simulations, which consequently leads to an improvement of the antenna efficiency and bandwidth. Subsequently, the MEMS PBG antenna is micromachined and measured, and the simulation characteristics are verified by the measured curves of the MEMS PBG antenna. The measured peak return loss of PBG patch antenna is -21dB at 5.36GHz, and the bandwidth of 8.5%, which is three times wider than that of the conventional patch, therefore the gain and the bandwidth are enhanced by means of PBG process.