Analytic description of disc diffraction model is obtained using elliptical pits model and Babinet principle. The influence of disc radial tilt on tracking servo system is analyzed and computed focusing on three common disc types. Tracking error offset caused by radial tilt is on DVD-ROM using DPD (Differential phase detection) method, 0.15 μm/° using push-pull method. Tracking error signal with DPD method exhibit analyzed better performance than push-pull method against disc radial tilt under the same disc parameters. Finally relationship between groove depth and tracking error signal offset of DVD-RAM disc is analyzed.