Abstract: Broadband and high-precision processing of offshore horizontal cable 3D data is receiving increasing attention in the exploration of lithological oil and gas reservoirs recently. However, specialized analysis and discussion are lacking. The broadband high-precision processing technology of 3D data of offshore horizontal cables was systematically summarized, and the procedures of broadband high-precision processing and key technologies of horizontal cables in shallow water area were established, including mainly the deghosting in horizontal cables, pre-stack integrated multi-domain denoising, shallow-water multi-wave combinational suppression, and target-based fine-velocity modeling and fine-migration imaging, etc. By applying real data on the western slope of Xihu Sag, the broadband, amplitude-preserving and high-precision seismic results with improved resolution were obtained. The reservoir inversion and geological evaluation carried out by the results are in good agreement with new drillings, from which the geological viewpoint obtained is more reasonable.