A full-transparent zone plate (FTZP), which can reuse the wave blocked in the focusing of the Fresnel zone plate (FZP), is proposed to improve the efficiency of terahertz (THz) focusing without aberration. We find that the substrate thickness of the FTZP has a great influence on the focusing intensity, which results from the Fabry–Perot effect. The focusing efficiency of FTZPs could be about twice as high as that of FZPs, but the widths of both focus spots are comparable with the wavelength. The experimental results are in good agreement with the simulation.