Measurements were made on the ratio of flesh in whole body and analysis of the nutritive composition, energy and amino acids of muscle in A. nigrocauda which is endemic fish living in the up reach Changiiang River. Samples were collected from the Longxi branch at Sichuan Luzhou in Mainland China during 2001-2002. Longxi branch is a first step tributary of the up reach Changjiang River. The ratio of flesh in whole body was measured by using 14 individuals. The nutritive composition, energy were analyzed by using 21 groups from 35 individuals. The composition of amino acids of muscle was examined by using 10 individuals. It was showed that the ratio of flesh to body was 70.74%, the ratio of gill in whole body was only 1.40%; analysis results of the nutritive composition (%, wet) were that : the moisture of muscle was 80.97%, protein 15.92%, fat 1.11%, ash 1.01%, non-nitrogen extract 0.99%. The content of energy was 4.37kJ/g, E/P was 27.45kJ/g. There was no apparent relationship between changes of body length and the content of the nutritive composition, energy and amino acids in muscle. There was no significant different in the content of the nutritive composition, energy and amino acids in muscle from the samples at May and October. It was found those 17 common amino acids and 9 essential amino acids for human needs in muscle( no analysis was made for tryptophane). The total content of amino acids was 69.07% (dry); the content of essential amino acids was 34.81%; the percentage of essential amino acids in total amino acids (E/TA) was 50.39%; essential amino acids to no-essential amino acids (E/NE) was 1.02; essential amino acids gram to total nitrogen gram (E/TN) was 2.59; except cystine, coefficient variations of content of amino acids were lower than 10%, the content of the different amino acids was stable. By nutrition evaluation for the amino acids in muscle to human needs, the content of 4 kinds delicious amino acids was 26.94%; according to the amino acids score (AAS), the first limited amino acid was threonine and the second limited amino acid was valine; on the basis of chemical score (CS), the first limited amino acids was valine and second limited amino acid was ileucine; the essential amino acids index was 63.64. Comparativing the contents of amino acids in muscle of Ancherythroculter with four species Culter, it was not obvious that the results were apparent difference.