Herein, we report the ultrasound-induced modulations of the morphologies and underlying molecular structures of tetrapeptide 1-D self-assembly. The self-assembly of the tetrapeptide (TTR108-111) precipitating out of the 1:1 mixed methanol/water is modulated from microtapes into nanotapes, nanofibers, and then bundles of nanorods when subjected to sonication for a period. The sonication-treated and untreated self-assemblies all give a set of equatorial pattern and a series of meridional pattern, indications of a typical "cross-beta-structure" as the core structural motif. FTIR data indicate that all the assemblies contain a mixed pattern of beta-sheets (dominant) and unstructured conformations (minor), and the relative proportion of unbound structures to beta-sheets is as a function of sonication time, suggesting an ultrasound-induced modulation of beta-sheet interactions. Accordingly, a possible model regarding a dynamic equilibrium between re-dissolution and re-assembling processes, e.g., a typical sonocrystallization process was proposed for such ultrasound-induced modulations of morphologies and underlying molecular structures.