In this paper, the antenna analysis simulator made by the object oriented programming was reported. This simulator based on a plug-in frame structure was composed by GUI, a FDTD solver and a Moment Method solver. These elements were combined in the plug-in frame by the API. This simulator can work with the solvers using the FDTD and the Moment Method under the identical GUI. Numerical results from each analysis method for a thin-wire antenna were compared.