Abstract: In this paper, the nutritional composition (crude protein, amino acids, crude fat, fatty acids, mineral elements, etc.) and safety index total volatile basic nitrogen (T-VBN), thiobarbituric acid (TBA), nitrite and biogenic amines, heavy metals, etc. in fermented mandarin fish (Siniperca chuatsi) muscle were tested. The results show that the contents of water and crude protein in the two fermented mandarin fish were lower than those of fresh ones, and the contents of ash, crude fat, umami amino acids (aspartic acid, glutamic acid and alanine), essential amino acids, total unsaturated fatty acids, sodium and calcium were all higher than those of fresh mandarin fish. The amino acid composition of the two fermented mandarin fish was similar. The contents of ash, crude fat, sodium and calcium in No.1 fermented mandarin fish were higher than those in No.2, while the contents of polyunsaturated fatty acid and crude protein were lower than those in No.2. In terms of safety, neither of the two fermented mandarin fish had excessive heavy metals, but the contents of TBA, T-VBN, nitrite and biogenic amines were higher than those of fresh mandarin fish. The contents of T-VBN and histamine in No.1 fermented mandarin fish were higher than those in No.2, while the contents of TBA, nitrite and total biogenic amines were lower than those in No.2. In general, fermented mandarin fish is a kind of fermented fish products with rich nutrition and high nutritional value. Besides, quality control technology should be used  to improve the quality of fermented mandarin fish.