Abstract: In this paper, measurements were made on the ratio of f lesh in whole body and analysis of the biochemical composition, energy and amino acids of muscle inM. pellegrini which is endemic fish living in the up rea ch Changjiang River. Samples of 45 individuals were collected from Longxi branch in Sichuan Luzhou in Mainland China during 2001—2002. Longxi branch is a first step tributary of the up reach Changjiang River. It was shown that the ratio of flesh in whole body was 70.74%,the ratio of gill in whole body was only 1.52% ; Analysis of the biochemical composition were the moisture of muscle 80.97%, p rotein 15.92%, fat 1.11%,ash 1.01%, non-nitrogen extract 0.99%, the conten t of energy was 4.37KJ/g, E/P was 27.45KJ/g. There was no apparent relations hip between changes of body length and the content of the biochemical composition, energy and amino acids in muscle. There was significant different in the contents of fat and non-nitrogen extract from the muscle samples at May-June and October. Comparativing the content of the biochemical compositions and calorific values in the three kinds fish ofM. pellegrini. Megalobrama amblycephala an dParabramis pekinesis,in the same season, same way getting material, it not show the difference about the contains of the biochemical composition, energy a nd amino acids of muscle in three kinds of fishes. The composition of amino acids of muscle was found those 17 common amino acids and 9 essential amino acids for human needs (no analysis was made for tryptophane ). In dry sample the total content of amino acids was 69.54%; the content of es sential amino acids was 33.07%; the percentages of essential amino acids in total amino acids were 47.55%; essential amino acids to no-essential amino acids( E/NE) was 0.91; essential amino acids gram to total nitrogen gram (E/TN) was 2.57; except histidine, tyrosine, threonine and cystine, coefficient variation of content of amino acids were lower than 10%, it was apparent that the content of the different amino acids was stable. Proceed the amino acids grade point to the fish muscle, that provides scientific basis for evaluate its protein quantity with guide the protein using of resource. According to nutrition evaluation, in the amino acids score (AAS) and chemical score(CS),the first limited amino acids was valine and second limited amino ac id was ileucine; the essential amino acids index(EAAI) was 61.75. In wet sample the content of 4 kinds delicious amino acids was 5.85%.