With precursor modification by regulating dianhydride hydrolysis degree, the viscosity of polyimide precursor solution, derived from 3,3',4,4'-biphenyl tetracarboxylic dianhydride (BPDA) and para-phenylenediamine (PDA), was facilely manipulated. The chemical structure of the precursor was characterized by infrared (IR) spectrometry and proton nuclear magnetic resonance (1H-NMR) spectrometry. The effects of dianhydride hydrolysis on the viscosity, imidization process and properties were investigated. The results show that the precursor can be formed from hydrolytic BPDA and PDA, with amide acid and carboxylic ammonium salt groups in the molecular structure. The viscosity of the precursor can be reduced by the introduction of carboxylic ammonium salt group, achieving the effective regulation of viscosity in the 10-105cP range. Importantly, the existence of carboxylic ammonium salt shows no influence on the complete imidization of the precursor, which guarantees the maintenance of mechanical property. Interestingly, the coefficient of thermal expansion (CTE) of this BPDA-PDA polyimide films can be reduced by this viscosity manipulation method.