Abstract: In a BR buffer medium of pH 3.06,an association complex was formed between streptomycin (SM) and pontamine sky blue (PSB),leading to appearance of a negative absorption spectrum with its absorption maximum at the wavelength of 622 nm,bathochromically shifted 10 nm from the positive absorption maxmum (612 nm) of PSB.Linear relationship between the values of increase in negative absorbance (-A) and concentration of SM was obtained in the range of 0.17×10-7-1.8×10-5mol·L-1 with the apparent molar absorptivity (ε622) of 1.06×104L·mol-1·cm-1.The proposed method was applied to the analysis of 3 samples of streptomycin sulfate injection,giving values of SM contents in consistency with the labelled values.Test for recovery was performed by adding standard SM solution to the injection samples,and values of recovery found were in the range from 99.1% to 101.3%.