The generation principles of L-tyrosine and its distribution in the fermentation tanks were studied by tracking the process of soy sauce fermentation.The results show that the quantity of L-tyrosine is different in winter and warmer under the influence of varied temperature,but the trend of L-tyrosine evolving is similar.In the early fermentation stage(first two weeks),there is almost no L-tyrosine separated out from suspension during winter.After a month of fermentation,about 0.15g/kg L-tyrosine was separated out.Another two weeks later,the quantity of L-tyrosine reaches 0.2 g/kg.At the fermentation terminal,0.23 g/kg L-tyrosine can be separated out.While in warmer seasons,the L-tyrosine particle is available in the mash after a week of fermentation.0.2 g/kg and 0.25 g/kg of L-tyrosine can be harvested from the suspension after a month of fermentation and when the process is terminated,respectively.The particle shapes in winter and summer are different.The distribution of different size particles varies.