In the present study, we calculate eight low-lying (1.3-1.7 eV energy region) electronic excited states in well accordance with the absorption and CD spectroscopic properties of PSRC from Rb. shpaeroides by using time-dependent density functional theory (TDDFT). Our present calculations demonstrate that, only when the interactions among the prosthetic groups have been taken into account, a set of satisfactory assignments for both absorption and CD spectra of PSRC from Rb. sphaeroides can be achieved simultaneously.