PURPOSE: To propose a new method to evaluate the values of intraocular lens (IOL) tilt and decentration with anterior segment optical coherence tomography (AS-OCT). METHODS: Based on postoperative anterior segment images of IOL from two patients, the values of IOL tilt and decentration were evaluated through curve fitting, image registration and basic geometric theories. RESULTS: The angles of IOL tilt were 2.200 degrees and 2.688 degrees respectively, and the length of IOL decentration were 0.555 mm and 0.474 mm, which were all credible, compared with clinical observations. CONCLUSIONS: Our Geometry-based method to evaluate the values of IOL tilt and decentration might be reasonable and simple with a good repeatability, which may be proved available in other circumstances — IOL implanting and evaluating the different effects on various types of IOL implantation.