Abstract: Common conversion point (CCP) gather extraction, involving P-wave incidence and S-wave reflection, is a key step in PS-wave seismic data processing. As geological structures in multicomponent seismic exploration become increasingly complex, conversion point calculation methods based on the horizontal interface assumption are no longer adequate for accurate imaging. In particular, under three-dimensional (3D) dipping interface conditions, traditional approaches require prior knowledge of multiple parameters—such as interface dip, azimuth, normal depth, and the P-/S-wave velocity ratio (v_P/v_S)—which are often difficult to obtain in advance, making CCP gather extraction challenging. Moreover, the absence of an exact analytical solution for 3D dipping interfaces may lead to significant errors in conversion point estimation. Based on the physical principle that different reflected wave modes image the same subsurface interface, we propose a novel 3D common conversion point calculation method for converted waves that does not require prior knowledge of interface geometry. The key idea is to extract the two-way traveltime of the target horizon from the P-wave stacked section and then compute its directional derivatives along local surface elements, which provide equivalent interface parameters for CCP positioning, thereby transforming the complex three-dimensional geometric localization problem into a scanning problem involving only the P-/S-wave velocity ratio. Tests on both synthetic models and real 3D three-component seismic data demonstrate that, compared with conventional methods that neglect interface dip, the proposed method provides a more reliable estimation of the v_P/v_S ratio and more accurate CCP positioning. The extracted CCP gathers produce stacked sections with improved continuity and clarity in dipping strata and facilitate direct comparison and joint interpretation with P-wave sections. The proposed approach offers a practical and efficient solution for 3D multicomponent PS-wave exploration in structurally complex areas.