An analytical method is presented for investigating the resonant behaviors of composed resonator formed by deporviting the c caxis oriented ＹＢａ2Ｃｕ3Ｏ７－δ (δ≈≈0) thin film on ＬａＡｌＯ3（００１）. The concept of the negative dielectric medium for a superconductor is introduced within the framework of the two-fluid model, which permits us to treat a superconductor as any other penetrable materials so as only its electromagnetic property is concerned. A conformal transformation is further suggested to map the original open boundary value problem to a closed one. This not only makes the original problem readily solved by using the variational technique, but also is powerful for the analyzing a kind of problems such as the propagation characteristics of the superconducting microstripe and coplannar waveguiding structures.