Abstract: The approach of 90° phase shift has been espoused as one of the core techniques in seismic-based sedimentology since 1998, when systematic researches were launched on the theories and application techniques of seismic-based sedimentology.However, its practical implementation is unsatisfactory.According to the philosophy of seismic prospecting, seismic events represent stratigraphic interfaces with impedance contrasts.The practice of 90° phase shift is intended to transform interfacial events into rock formations.Subsurface complexities often show as frequently interbedded thin layers, the interfaces of which could not be one-to-one correlated with seismic reflections as per forward modeling.This means that a reflection is the combination of seismic responses from a certain number of thin layers.Due to the limitation of seismic resolution, the operation of 90° phase shift cannot convert seismic data from interfacial events into lithologic sections; besides, such an operation is geologically meaningless and cannot yield good results for structure and lithology interpretation.Consequently, it may not be treated as a key technique in the study of seismic-based sedimentology, as it neither improves resolving power of seismic data nor yields lithologic sections from seismic sections.