A metamaterial composed of two face-to-face symmetrical split-ring resonators and a cross-wire located on each side of a dielectric substrate is demonstrated. The retrieved refractive index from the scattering parameters show that the proposed structure can exhibit a broadband negative refraction passband from 41GHz to 62GHz with very low dispersion from 47GHz to 57GHz. In addition, the retrieved refractive index is examined by Kramers-Kronig relations. The metamaterial with such a broadband negative index and low dispersion will be valuable and applicable in the wavelength division multiplex system.