Natto， which contains several functional components such as nattokinase， can prevent cardiovascular disease， but its ammonia odor greatly reduces its acceptance by Chinese people. In order to decrease the ammonia production during natto fermentation， this study compared the inhibitory effect of four reagents on glutamate dehydrogenase， a key enzyme for ammonia production by Bacillus subtilis var. natto， and found that tea polyphenols (TPP) had the highest inhibitory activity. TPP acted as a substrate-competitive inhibitor， the IC50 value was 20.60 μg/mL and it could enter the cells of Bacillus subtilis var. natto. Therefore， it was expected to be used as an additive to reduce the production of ammonia during the fermentation of natto. Then， the optimal process， which was adding 4.16 mg/g TPP at 11th hour of fermentation， was determined by analyzing the bacteria growth curve， the ammonia production during the fermentation of natto with and without addition of TPP. The results showed that the ammonia production was reduced by 63.90% under the optimal condition， while there was no significant negative effect on nattokinase activity. Finally， the sensory evaluation results showed that the ammonia smell and flavour of natto was significantly reduced by adding TPP， and therefore the acceptance was increased. All these results showed that TPP had great application potential in natto production.