A wavefront aberration measurement method for freeform spectacle lenses in real viewing condition is proposed based on the human eye-spectacle lens model. The method is different from the existing focimeter and the Hartmann-Shack wavefront aberration measurement method in which the wavefront aberration on the back surface of spectacle lenses is measured. The principle of wavefront aberration measurement for spectacle lenses on its vertex sphere in real viewing condition is demonstrated. Based on the principle, the corresponding experimental measurement apparatus is designed and built. Experiments of scanning and measuring spectacle lenses are carried out to obtain the wavefront aberration and wearer power on the vertex sphere. The measurement results verify that wavefront aberration measurement for freeform spectacle lenses in real viewing condition can be achieved by the proposed method. The findings assist in evaluating the manufacturing and image qualities of freeform spectacle lenses. The results also guide design and optimization of the lenses.