Abstract: It is difficult to identify the channel sand bodies of the H3b1 layer of Huagang Formation in the Y area, East China Sea Shelf Basin. The study area covers 1200 km² with only 11 drilled wells, resulting in a sparse well network. Thin reservoirs exhibit rapid lateral variations, and conventional stratum-slice attributes suffer from the time-transgressive effects, leading to poor reliability in well-to-well correlation and making it difficult to finely characterize sedimentary facies. To address the above problems, this study adopted a seismic sedimentology workflow based on high-precision 3D seismic data. Specifically, 90° phase correction was applied to convert seismic reflection interfaces into lithological response interfaces, suppressing the time-transgressive artifacts. Combined spectral decomposition with multi-band RGB (red green blue) fusion, frequency bands sensitive to thin beds are selected to improve channel boundary identification, and integrated with well-log facies to calibrate seismic attributes. As a result, four NE-SW trending distributary channels are successfully identified in H3b1 layer. Practical application demonstrates that this method effectively improves the identification accuracy of complex channel sandbodies, and the newly identified channels provide a reliable geological basis for the newly proven natural gas reserves in the study area.