TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation (claimed): Tin-containing benzothiophene compound of formula (A), dibromobenzothiophene of formula (B) and 5,8-dibromo-quinoxaline of formula (C) are mixed and subjected to Stille coupling reaction in presence of organic solvent and catalyst under water-free and oxygen-free environment, to form conjugated polymer (I).m=i+j;andi=0 to less than m.Preferred Process: The 5,8-dibromo-quinoxaline compound (C) is obtained by reacting dione compound of formula: R3-C(=O)-C(=O)-R2 and thiophene-3,4-diammonium dichloride in solvent at 0-78 degrees C for 1-24 hours, adding weak alkali, forming quinoxaline derivative of formula (F), reacting the obtained quinoxaline derivative with chloroform and acetic acid at 0-70 degrees C, adding n-bromosuccinimide to the reaction mixture, and reacting for 1-48 hours. The purification process of conjugated polymer is carried out by dripping the conjugated polymer to methanol, filtering, washing with methanol, drying, obtaining gel of conjugated polymer, dissolving the gel of conjugated polymer in toluene, and adding toluene solution to the aqueous solution of sodium diethyldithiocarbamate, carrying out chromatography in a aluminum peroxide column, separating the conjugated polymer, leaching by chlorobenzene, removing organic solvent under vacuum conditions, and extracting the conjugated polymer by Soxhlet extraction method using propanone. The reaction is performed at 60-130 degrees C for 24-72 hours. Preferred Composition: The molar ratio of dione compound and thiophene-3,4-diammonium dichloride is 1:0.1-1:10. The content of weak alkali is 2-50 times the content of dione compound. The solvent is chosen from methanol, ethanol and ethyl acetate. The weak alkali is triethylamine and/or sodium carbonate. The organic solvent is chosen from tetrahydrofuran, ethylene glycol dimethyl ether, benzene, chlorobenzene and toluene. The content of the catalyst is 0.05-60%. The catalyst is organic palladium, or mixture of organic palladium and organic phosphorus ligand. The organic palladium is tris(dibenzylideneacetone)dipalladium(0), tetrakis(triphenylphosphine)palladium or bis(triphenylphosphine)palladium chloride. The organic phosphorus ligand is tri(o-tolyl)phosphine. The molar ratio of organic palladium and organic phosphorus ligand is 1:2-1:20.