In this study, the characteristic of the designed porphyrin sensitizer was studied by density functional theory (DFT) and time-dependent density functional theory (TDDFT). D-pi-A sequence of seven donor-acceptor dyes A-F in the organic dye-sensitized solar cell (DSSCs) was analyzed. Firstly, the structure and frequency of porphyrin dyestuffs with different substituents were optimized by DFT method, and the structure and properties of the ground state of porphyrin dyes were studied by comparing the energy differences of different orbitals. Then, the TDDFT method was used to study the porphyrin molecules with different pi bridge. The structure and properties of the excited state are discussed in terms of the energy and charge separation state of the molecular orbital of the porphyrin sensitizer. According to the absorption spectrum, the characteristic of the light absorption for the sensitizer molecule is investigated. The results shown that the key characteristic parameters closely related to the open circuit photovoltage (V-oc) and the short circuit current density (J(sc)) of the porphyrin sensitizers helped to clarify different pi bridges. The change of V-oc and J(sc) affected the energy level change of the porphyrin sensitizers with different pi bridge. Finally, a suitable pi bridge was selected as a porphyrin sensitizer candidate with higher conversion efficiency.