Nutritional composition and gender defferences of adult mysis are important for the evaluation of nutritional value and the understanding of broodstock nutrition requirement for Neomysis japonica. In order to compare the nutritional composition between the males and females of adult mysis N. japonica under the feeding formulated diets, this study was conducted to detect and compare the the proximate composition, lipid classes, fatty acid and amino acid compositon between the adult males and females as well as the formualted diet by the culture experiments and biochemical analysis. Independent T-test was usded to examine the differences between males and females, while P <0.05 was regareded as statistically significant differences. Moreover, the relative retention ratios (animal tissue contents/dietary contents) were further analyzed on the poly-unsaturated fatty acids (PUFA) and essential amino acids (EAA) for both males and females. The results showed that, (1) The crude protein and crude lipid of the formualted diet were 40.48% and 9.82% respectively, while the content of high unsaturated fatty acid (HUFA) and DHA/EPA ratio were 27% and 1.34, respectively (Table 1). The contents of total amino acids (TAA) and ten essential amino acids (EAA) were 38.80% and 16.32% respectively (Table 1). (2) The mositure content of males and females was around 88%, and no gender difference was found for them (Table 2). However, the adult females had the significantly higher contents of crude protein, crude lipid and triglyceride than the adult males, while the males had the higher phospholipid levels than the females (Table 2). (3) Except for 14:0 and 16:1n-7, the adult males and females had the similar compositions for the saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) (Table 3). The adult males had the higher percentage of ARA, EPA, DHA, ∑HUFA and the DHA/EPA ratio than the adult females, while the females had the higher LOA, LNA and 18:4n-3 levels than the males (Table 3). As for the amino acids, the females had the higher contents of EAA, TAA, isoleucine, leucine, phenylalanine, threonine, arginine, cysteine, aspartic acid, serine and glutamate than the males, while the adult males had the significantly higher taurine levels than the females (Table 3). (4) The adult females had the higher relative retention ratio of LOA and LNA and the lower relative retention ratio for ARA, EPA and DHA than the adult males, but the relative retention ratios of EAA were close between the adult males and the females (Table 4). In conclusion, adult N. japonica had the gender differences on the levels of crude protein, crude lipids, triglyceride, phospholipids, some fatty acids, some amino acids and the relative retention ratios of some fatty acids between adult males and females, which may indicated adult females and males had the different nutritional requirement.