A 3D-dual circular metamaterial structure (3D-DCMS) is proposed to characterize the effective permittivity, effective permeability (effective parameters) and refractive index. The 3D-DCSRR consist of an outer ring, dual inner ring, which are connected by metallic vias. The structure is embedded to substrate which has a 0.1mm vertical distance to the dual inner ring. The proposed structure has a negative permeability at 2.075GHz. Therefore, an effective parameters >0 and μ<0, resulting 3D-DCSRR as MNG metamaterial and the refractive index is negative. © 2019 IEEE.