3D FDTD methods to model dielectric with arbitrary shapes and thin perfect conductor surface were put forward in this paper.Dielectric was modeled by the average electrical parameters corresponding with component location in mesh.By introducing auxiliary electric and magnetic fields

the modeling of thin metal curved surface was implemented.Dielectric resonators and a conical horn antenna were calculated by the presented methods.The correctness of the methods were showed by comparing the results with those reported in the published papers

and the validity of the modeling methods were also justified.