The main objective of this study was to investigate the characteristics changes of intramuscular collagen of beef muscle after marinated with three weak organic acids(lactic acid,acetic acid and citric acid) and NaCI.Beef Semitendinosus muscle was marinated at 4℃ for 24 h in 2% NaCl solution with 1.5% lactic,acetic and citric acid solutions respectively.The changes of heat-insoluble collagen contents and amino acids composition of collagen from beef muscle during processing were analyzed.The results indicated that there were no significant difference(P>0.05) for heat-insoluble collagen extraction rate between the various marinated meat samples and control group.Compared with the control group(82.06 g/100g),the total amino acid(TAA) content of collagen in various marinated meat samples was decreased,and the TAA contents of collagen in meat marinated with three weak organic acids alone were lower than combined with NaCl.The amino acids content in collagen from beef muscle was varied in different marinated groups,indicating the impact of marinating on its composition.