In this study, novel porphyrin-based dye sensitizer with diphenylamine (DPA) as the electron donating group, isoindigo (II) as the electron withdrawing group, and carboxylic acid (CA) with benzene as the anchoring part (YD2-II-CA) were theoretically investigated in comparison with the recent best dye (YD2-o-C8). Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations were used to gain insight into the factors responsible for photovoltaic performance. Due to the substitution of the electron withdrawing unit, the absorption spectra of YD2-II-CA was more red-shifted and broader than the spectrum of the YD2-o-C8. The results suggest that this novel porphyrin-based dye would have good photovoltaic properties in dye-sensitized solar cells (DSSCs)