In recent years, reconfigurable antennas have been studied by several research organizations since their high performance (the ability to change the range of frequency, the direction of radiation, and so on) is extremely attractive and useful for many applications [1], [2]. As switching elements, semiconductor switches, that is, a PIN (p-intrinsic-n) diode or an FET (field effect transistor) and an RF-MEMS switch are assumed to be integrated with the antenna. The latter switch has the advantages of miniaturization, lower power consumption, and much lower transmission losses when the MEMS process is used. In addition, by using the MEMS process, switches that are integrated on the body of an antenna can be easily manufactured. Based on these advantages, MEMS-based reconfigurable antennas are found to be excellent for facilitating mass production and providing low costs. In a previous study, we proposed a polarization-reconfigurable U-slotted patch antenna that can switch between two orthogonal polarizations by means of cantilever switches loaded on portions of a slotted patch antenna [3]. In addition, the feasibility and effectiveness of this antenna were verified by the results of a simulation and experiment. This study aims to realize a reconfigurable antenna with a higher performance, particularly with respect to the characteristic of electric power resistance, for which the improvement in the proposed antenna structure is studied by simulations. First, the geometry and basic operation of the antenna are presented. Next, the current distribution on the antenna surface is analyzed by a simulator. The result of this analysis is compared with that of the test for the electric power resistance conducted using the prototype. Finally, an improved structure that can withstand a large input electric power is developed.