Intoduction: ChuanKeZhi, an intramuscular Traditional Chinese Medicine injection, has been used to treat asthma for more than twenty years in China and good clinical results have been received. However, the material basis remains to be elucidated. Materials and Method: Aiming at disclosing the antioxidants in ChuanKeZhi, an online identification system adopting high performance liquid chromatography tandem chemiluminescence detector was carried out. Two lignanosides named (-)-olivil-4'-O-glucopyranoside and (+)-cycloolivil were proved to be mainly responsible for scavenging hydrogen peroxide, and their structures were confirmed by NMR data. Chemiluminescence inhibition was calculated as the ratio of the maximum intensity in the presence of injection to that in its absence, and logarithmic values of inhibition ratio showed a good linear correlation with the concentrations of cycloolivil in the range of 4.950-158.3 mu g/mL (R-2 = 0.9917). Principal component analysis disclosed that contents of these two compounds explained mostly the variance of total antioxidative activities of different batches. Result: This work revealed the components contributed to antioxidative activity of ChuanKeZhi injection and might provide some information for new drug development and better quality control method.