A systematic design idea for liquid-filled cylindrical zoom lenses with ideal imaging quality over a wide focal length range is introduced in detail. The PWC method is used to calculate the initial structure parameters of the zoom lenses, and the optical design software ZEMAX is used to eliminate the spherical aberration at different focal lengths. Lenses named SLCL-Doublet are finally designed, which are formed by a symmetric liquid-core cylindrical lens (SLCL) filled with variable refractive index (RI) liquid and a doublet cylindrical lens capable of significantly weakening the spherical aberration. The focal length of the SLCL-Doublet continuously decreases from 101.406 mm to 54.162 mm as the liquid RI changes from 1.3300 to 1.5000. Calculated over 75% of the full aperture, the root mean square (RMS) spot radius of the SLCL-Doublet is always less than 7 µm over the whole focal length range, and the peak-to-valley wavefront error remains below the λ/4 limit when the focal length ranges from 62.373 mm to 65.814 mm, within which the lenses approach the diffraction limit, demonstrating improvement in the optical performance over that of previously designed liquid-core cylindrical lenses. The sources of potential fabrication and installation errors in the practical implementation of the SLCL-Doublet are also analyzed in detail. The SLCL-Doublet is demonstrated to be characterized by high imaging quality and easy installation, which enriches the types of core optical element for measuring the liquid RI and liquid diffusion coefficient and provides guarantee for improving the measurement accuracy.