The invention provides a pure organic dye containing conjugated units of different heterocyclic rings and derivatives thereof and application thereof in a dye-sensitized solar cell. The pure organic dye belongs to molecules of a D-phi-A structure. Segments of a donor, a phi conjugated system and a receptor are properly adjusted and controlled respectively to form the pure organic dye with wide spectral response and high molar extinction coefficient. The absorption spectrum of the pure organic dye is over 570 nanometers already close to the absorption of ruthenium dye; and when the pure organic dye is applied to the dye-sensitized solar cell, the photoelectric conversion efficiency of more than 10 percent is obtained, so the dye is the current most efficient and stable pure organic dye.