Abstract: Based on the high resolution 3D seismic data,seven submarine canyons are studied on their morphological and sedimentary characteristics in a block in the Baiyun Sag,northern South China Sea.Upon morphological features,the canyons are divided into three segments,namely upper,middle and lower segments.According to the continuity and amplitude of the reflection,integrated with seismic reflection configuration,the basal erosional discontinuity and two seismic facies,i.e.thalweg facies and slide facies,were recognized.The upper reach of a canyon is an erosional area characterized by the erosional discontinuity.In stead,the lower reach is in fact a depositional area,while the middle reach is characterized by the coexistence of erosional and depositional features.A depositional model for the submarine canyons in the Baiyun Sag is proposed as the results of the study.