By taking two tetramers as an example, we analyzed in detail the influences of vibronic couplings and the intermolecular interactions to their spectra. When the vibronic coupling is involved, the calculated vibrationally-resolved spectral width increases obviously, and the relative peak intensities coincide with those of experimental spectra very well. The electronic absorption spectra of two tetramers don't demonstrate more obvious vibrational progressions than that of the monomers because the exciton coupling in the aggregate is stronger than the nuclear reorganization energy, leading to quenching. However, in the ECD spectra, this sophisticated spectral structure reappears, which is crucial for the conformation identification.