Abstract: An improved ammonia-iodometry is developed to determine the concentration of copper in a high silver-bearing copper concentrate in Hechi, Guangxi Region. Samples are dissolved by hydrochloric acid-nitric acid-bromine system, and then an appropriate amount of hydrochloric acid is added to eliminate the residual contamination of high content of silver. The pH value of the solution is regulated by ammonia-acetic acid. The concentration of copper is finally determined by titration with standard solution of sodium thiosulfate. Satisfactory results are obtained.