Abstract: The laboratory preparation of 3,3′,4,4′-biphenyltetracarboxylic anhydride, which is an important monomer of polyimide, was investigated.The improvement of the synthesis method was on the halogenating reaction of o-phthalic anhydride and the dehalogenation-dimerization of monosodium 4-bromo-o-phthalate.The circulation of the catalyst was discussed.The optimal reaction conditions (solvent,temperature, time, yield)were as follows, brominating: water, 75 ℃,4 h, 78%; dehalogenation-dimerization: water, 100 ℃, 3 h, 90.4%; cyclization: acetic anhydride, reflux, 2 h, 97%.High purity product was obtained with overall yield of 68.4%.