The focal length, curvature radius, and refractive index of a lens are important parameters that characterize the lens’ performance and are essential for selecting lenses in optical design. This study proposes a lens parameter measurement method based on the Shack-Hartmann wavefront sensor (SHS). First, the reference point for measuring the focal length of the lens under test is determined by evaluating a function that calculates the sum of the least squares of the centroid offsets of the light spots formed by the SHS (LSSCS). The focal length of the lens can then be obtained by measuring the curvature radii of two spherical waves at two different distances from the reference point. The curvature radius of the lens surface is then calculated by determining the coordinate difference between two specific positions. These positions correspond to the points at which the reflected light beam on the lens surface becomes parallel to the incident beam, as determined by the LSSCS evaluation function. Finally, for thin lenses, the refractive index of the tested lens material is calculated using the lens manufacturer’s formula based on the measured focal length and surface curvature radius. The experimental results demonstrate that the lens parameters measured by the proposed method are in excellent agreement with the nominal values. The proposed method offers several advantages, including simplicity, accuracy, and resistance to interference, while eliminating the need for wavefront reconstruction.