The invention relates to a benzo[1,2-c,4,5-c']dithiophene-4,8-dione (BDD)-based electron acceptor, synthesis of an oligomer photovoltaic donor material with a (D-A)n+1D (n is equal to 1,2. . .) framework as well as application of the oligomer photovoltaic donor material to an organic solar battery. The oligomer comprises thiophene, benzene, benzodithiophene and a derivative electron donating (D) unit as well as BDD and a derivative electron acceptor (A) unit, and can serve as a donor material widely applied to a solution processing type organic solar battery. When a light active layer donor material is 5 BDTBDD, an acceptor material is 3,9-bis(2-methylene-3-(1,1-dicyanomethyl)indolone)-5,5,11,11-tetra(4-hexylphenyl)- dithiolato[2,3d,2',3'd]-s-indole[1,2-b,5,6']dithiophene (ITIC), and the highest energy conversion efficiency of bulk heterojunction oligomer solar energy is 7.89 percent when the mass ratio of the donor to the acceptor is 1,0.8. The organic solar battery is constructed bytaking the oligomer as the electron donor material and non-fullerene as the electron acceptor material, and efficient energy conversion of the device is realized.