TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Composition: The dehydrofluorination agent is alkali metal hydroxide.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation (Claimed): The fluorine-containing aromatic compound (I) is obtained by carrying out condensation reaction of aromatic compound of formula (II) and fluorine-containing aromatic compound of formula (III) in presence of dehydrofluorination agent.X=H, CH3CO, CH3CH2CO, (CH3)3C(CH3)2Si, or (CH3)3Si;andor c+n=0-6.Preferred Composition: The aromatic compound (II) is preferably 4-ethenylphenol or 4-ethenyl-1-acetoxybenzene. The fluorine-containing aromatic compound (III) is preferably perfluorobenzene, perfluorotoluene, perfluoroxylene, perfluorobiphenyl, perfluoroterphenyl, perfluorotriphenylbenzene, perfluorotetraphenylbenzene, perfluoropentaphenyl benzene, perfluorohexaphenyl benzene, 1,1'-oxybis(2,3,4,5,6-pentafluorobenzene), 1,1'-thiobis(2,3,4,5,6-pentafluorobenzene), bis(2,3,4,5,6-pentafluorophenyl)methanone, 1,1'-sulfonylbis(2,3,4,5,6-pentafluorobenzene) or 1,2,3,4,5-pentafluoro-6-((2,3,4,5,6-pentafluorophenyl)sulfinyl)benzene. Preferred Property: The fluorine-containing aromatic compound has molecular weight of 300-2000. Preferred Definitions:    R1-R4,Y'1,Y'2=H.    SPECIFIC COMPOUNDS - 2 Fluorine-containing aromatic compounds are specifically claimed i.e. 1-(4-ethenylphenoxy)-4-(4-(4-ethenylphenoxy)-2,3,5,6-tetrafluorophenyl)-2,3,5,6-tetrafluorobenzene of formula (Ia), and 1,3,5-tris(4-ethenylphenoxy)-2,4-difluoro-6-(trifluoromethyl)benzene.    EXAMPLE - 82.2 g Perfluorobiphenyl and 98.4 g p-acetoxystyrene were dissolved in 708.9 g dimethylacetamide, then potassium hydroxide aqueous solution was added, stirred, and the resultant product was reacted for 24 hours. The reaction crude liquid was dripped in 3090 g 0.5-N hydrochloric acid, the resultant product was precipitated, filtered, and washed with ion-exchange water 2 times to obtain 1-(4-ethenylphenoxy)-4-(4-(4-ethenylphenoxy)-2,3,5,6-tetrafluorophenyl)-2,3,5,6-tetrafluorobenzene with yield of 92.8%.