In order to evaluate the composition of amino acids and contribution to amino nitrogen in fermented soy sauce; three products in different levels were analyzed. Results showed that there were various amino acids; and high essential amino acids proportion in fermented soy sauce; and contribution of Free amino acids (FAAs) and oligopeptides to amino nitrogen (AN) distributed equally in no umami enhancer addition samples. Exogenous sodium glutamate can significantly improve the content of AN. FAAs content of the three samples (1#: premium soy sauce without umami enhancer addition; 2#: premium soy sauce with umami enhancer addition; 3#: three grade soy sauce without umami enhancer addition) were 3.875 g/100 mL; 6.041 g/100 mL and 2.341 g/100 mL; respectively; but 1# became the highest one with value of 3.494 g/100 mL; which was 14.11% and 65.91% higher than sample 2# and 3#; after excluding glutamic acid. Essential amino acids content of 1# was the highest with value of 2.08 g/100 mL; which was 18.18% and 85.71% higher than sample 2# and 3#. AN content of 2# was highest 1.42 g/100 mL; that glutamic acid gave 40.14% contribution in all. FAAs and AN content of 3# were the lowest. Research showed that the FAAs and AN composition analysis might be benefit to fermented soy sauce evaluation.