Konjac glucomannan and gallic acid were used as the raw materials to prepare gallic acid konjac glucomannan. The effects of the amounts of N,N'-Diisopropylcarbodiimide and 4-dimethylaminopyridine,mass rate of triacetyl gallic acid and konjac glucomannan,reaction temperature and reaction time on the esterification reaction were investigated through single factor and orthogonal experiments. The results showed that optimal reaction conditions were determined as follows: mole rate of triacetyl gallic acid,N,N'-Diisopropylcarbodiimide and 4-dimethylaminopyridine was 1∶ 1. 5∶ 0. 1; mass rate of triacetyl gallic acid and konjac glucomannan was 2∶ 1; reaction temperature and reaction time were 100 ℃ and 4 h respectively; and the average degree of esterification of triacetyl gallic acid konjac glucomannan was 0. 593. In contrast with konjac glucomannan,both viscosity and stability of the hydrosol of modified konjac glucomannan product were remarkably improved.