Solar energy,in theory,should be the answer to all our energy problems.It became the truth since Prof.Gr(a)tzel invented the third generation of solar cell,the so-called Gr(a)tzel Cell in 1991[1],which paves the way for us to use solar energy as the replacing energy resource in near future.The Ru(II)complexes [Ru(bpp)(dcbpy)Cl]+,[Ru(tcbpp)(bpy)Cl]+ and [Ru(tc`bpp)(bpy)Cl]+ dye molecules are studied theoretically using DFT techniques to explore their properties as dye in solar cell.The calculation results indicate which sites the COOH groups attach can significantly influence the electronic structure of the dye[2].By migrating the COOH groups from the bpy ligand to bpp ligand,the nature of LUMO changes from bpy-localized to bpp dominated.The calculated low-lying absorptions at λ > 370 nm of the three complexes are categorized as metal-to-ligand charge-transfer(MLCT)transitions and the transition terminates at the orbital populated by the COOH appended ligand.The atomic spin density analysis also indicates that the ligand which is modified by the COOH groups is the ideal spot for the captured electron to situate.It can be predicted that the performance of dye-sensitized solar cell can be enhanced.For the porphyrin derivatives and organic molecular sensitizers are also investigated,and we have also new idea to improve the DSSC Efficiency via molecular design.The influencing factors(e.g.different TiO2 films conformation,electrolyte,electron injection mechanism,etc.)were also taken into account based on the assured theoretical model for the consideration of device environmental amelioration.