Using o-m-terphenyl, biphenyl instead of benzene as monomer, AlCl3 as catalyst, CuCl2 as oxidant, in the molten state, react at 100-200 ℃ for 3-4h to obtain branched polyphenylene. The reaction products are successively extracted with 10% benzene, mixed solvents of 90% naphtha and chlorobenzene, and the components and insoluble substances with low molecular weight are removed respectively, and the molecular weight is 500-3000, which can be dissolved in organic solvents such as chlorinated hydrocarbons. The yield of soluble polybenzene can reach about 30%, and the chlorine content is 1.0%-2.5%. It is a relatively pure polybenzene with high thermal stability.