Based on the theory of resonant-type left-handed materials, a novel structural unit of left-handed materials with broadband and low loss is proposed. By using the Nicolson-Ross-Weir algorithm and the Ansoft HFSS software, the equivalent permittivity, the equivalent permeability and the equivalent refractive index of the structural unit are obtained. The results show that the proposed structural unit has a low loss characteristic. In the frequency range of 23-32.3 GHz, both the equivalent permittivity and the equivalent permeability of the proposed structural unit are negative, meanwhile, the real part of the equivalent refractive index is negative while the imaginary part is close to zero. The proposed structural unit can provide a certain reference for the design and application of left-handed materials in the Kα band.