Effects of cladding size changes on electric conductivity of copper-aluminum-copper cladding plate were examined by the FEM （finite element method） software.It is found that with a fixed loading,electric conductivity of copper-aluminum-copper cladding plate is increased with increasing in copper thickness.However,with copper thickness more than 0.5 mm,effects of copper thickness on impedance of cladding plate can be neglected.At a fixed cladding width,with increasing in cladding thickness,impedance of the cladding plate is greatly decreased,while effects on electric conductivity are slowly weakened.At a given copper thickness,with increasing in cladding thickness,impedance of the cladding plate is decreased,and with increasing in width of cladding plate,effects of thickness on impedance of the plate are greatly weakened.