Abstract: Metamaterials are artificial structures exhibiting novel electromagnetic properties but not commonly found in nature, and they are generally known as left\|handed materials with simultaneously negative permittivity and permeability. Much progress has been made during the past few years on the development of metamaterials based on the transmission\|line mechanism since it was first proposed in 2002. The structure, preparation, principle of operation and properties of several typical transmission\|line metamaterials are discussed.