Abstract: It was found that the intensity of weak chemiluminescence (CL) produced by the reaction of dextromethorphan hydrobromide (D-MPHB) with KMnO4 in 5.0 mmol·L-1 H2SO4 medium was strongly enhanced in the presence of appropriate amount of Na2SO3,and linear relationship between the magnitude of relative CL intensity and concentration of D-MPHB was obtained in the range of 1.0×10-5-1.0×10-2g·L-1 with a detection limit (3S/N) of 3.5×10-6g·L-1.Base on these facts and by using the flow injection technique,a new method of FI-chemiluminescence determination of D-MPHB in its preparations was proposed.In its application to the analysis of a sample of dextromethrophan hydrobromide nasal drops,the contents of D-MPHB found were in consistency with the labelled value,and tests for precision and recovery were made on the base of this sample,giving values of RSD′s (n=5) less than 1.5% and of recovery in the range of 99.7%-102.8%.