Based on the technique of reducing working frequency of split ring resonators (SRR)，this paper presents a miniaturized left-handed metamaterial transmission line unit，and retrieves the effective permittivity and permeability parameters from the transmission and reflection data. To verify the presence of the left-handed frequency band，3D numerical simulation is conducted to an array of left-handed metamaterials including eight units，which demonstrates that the left-handed metamaterial microstrip line can support unique backward wave property very well. Compared with conventional left-handed microstrip lines，this structure has been reduced by 60% in electrical sizes，and would be more convenient for fabrication in applications as miniaturized planar circuit components.