Abstract: An electromagnetic simulation software is developed. The software is based on the finite-difference time-domain (FDTD) method and can handle objects with curved surfaces and edges.The program includes a Visual Basic(VB) graphical user interface for graphically inputting object geometries and setting source and boundary conditions, and uses Fortran language to compute with a data file from VB. Examples that show the applications of the software for antennas and resonators are presented, and the results show good agreement with those reported in the published papers.