Abstract
Complex conductivity of superconductor (CCS) is a principal parameter in the case of estimation for surface impedance of superconductor. Usual investigation on CCS is based on two fluid model, which is constructed on the assumption that electron pair has not collission with phonon. However, real part of CCS that derived from above two fluid model are not agree with measured values. We formulate modified two fluid model provided that moving electron pair has characteristic of equivalent loss which depend on high frequency electric field, and both density of super and normal electron are related by Rate equation. Furthermore, CCS is formulated by using modified two fluid model. Finally, numerical results of real part of CCS which obtained by modified two fluid model are agree with measured values.