A liquid-core-zoom cylindrical lens has been fabricated, which is used to measure accurately the refractive index of liquid filled into the core region of the cylindrical lens. The focal length of such a cylindrical lens varies with the refractive index of core liquid, which can be known by measuring experimentally the related focal length. Due to a high sensitivity in measuring refractive index and a short depth of field, a high accuracy in measurement of refractive index is ensured. The accuracy of refractive index for one single measurement is better than 0.0002 in the range of 1.3~1.642, when a 20× objective is used in a reading microscope. By either enhancing sensitivity of refractive index of the cylindrical lens or enlarging effective numerical aperture of the measurement system, the accuracy of refractive index can be further improved.