An improved planar structure of left-handed (LH) metamaterial is presented, and then designed and analyzed in microwave regime. In the anticipated LH frequency regime, the LH property is validated from the phenomena of backward wave propagation and negative refraction. To characterize the electromagnetic property of the planar metamaterial, we introduce the wedge method by constructing a wedge-shaped bulk LH metamaterial by stacking the planar LH metamaterials. The effective refractive index estimated by the wedge method is in excellent agreement with that retrieved by the inversion method from the transmission and reflection spectra.